Is choosing a different class feature too good as a (house rule) replacement for a redundant feat?

Question

In the group I DM for there was a player playing a 5th level Rogue / 4th level Assassin. He gained another Assassin level and he would have received Improved Uncanny Dodge, but he already had the ability, since both his Rogue and his Assassin levels granted him Uncanny Dodge.

In What can I do with an existing feat that I later get free as a class feature? it says that you just lose the feat. I don't like this though, so we generally rule that you get to pick a replacement feat.

In this case though, I allowed him to choose on of the Rogue special abilities, since it seemed appropriate for the class combination. What I want to know is, is being able to choose a Rogue special ability too strong as a replacement?

Answer 1

A rogue special ability is fair

Rogue special abilities are about equivalent to a feat (and, in fact, the feat option is one of the best of the options presented), and Improved Uncanny Dodge is something you generally can’t get as a feat.¹ Improved Uncanny Dodge definitely would not be a strong feat, but far weaker feats exist, and many of the rogue special abilities are even weaker.

You cannot generalize about class features’ value, however

The title question is unanswerable: class features vary widely in power. You can probably find something equitable to give in most situations like this, but it has to be carefully chosen on a case-by-case basis; you cannot make a blanket statement.

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1. ^{Arguably, you could use Shape Soulmeld for impulse boots, which grants Uncanny Dodge and is thus arguably sufficient to get Improved Uncanny Dodge if you already have Uncanny Dodge. But the impulse boots do not mention upgrading the way most sources of Uncanny Dodge do.}

Answer 2

If the house rule's gamed, there's a chance of a minor imbalance

The special ability uncanny dodge scaled differently in Dungeons and Dragons, Third Edition, where it was tied to, of all things, what's now the special ability trap sense. Advancing uncanny dodge meant looking at the rogue's level advancement, computing a character's effective rogue level based on how many levels the character had in classes the grant the special ability uncanny dodge, and, from that, first gaining improved uncanny dodge then an increasingly higher bonus to trap sense. Yay?

But Dungeons and Dragons 3.5 changed this, granting the special ability improved uncanny dodge when uncanny dodge was gained a second time, yet providing no mechanism for advancing improved uncanny dodge, therefore leaving bereft a PC who receives three or more iterations. Boo. Hiss.

I mention this because that makes reasonable your instinct to want to give the character something despite the game saying the character gets nothing, the system at one point having supported (albeit poorly) your instinct. My guess is the decision to streamline uncanny dodge—like a handful of other Third Edition to 3.5 changes—was made hastily and insufficiently considered, and I respect wanting to correct that error.

Anyway, nobody likes leveling up an getting nothing. The proposed house rule seems like a good one, even if it's ruthlessly exploited. Just in case the full ramifications haven't been considered, below's an example of a possible ruthless exploitation.

| Character Class        Uncanny  |
|   Level   Level         Dodge   |
|---------------------------------|
|    1st    Rogue 1         N     |
|    2nd    Barbarian 1     N     |
|    3rd    Rogue 2         Y     |
|    4th    Barbarian 2     Y     |
|    5th    Survivor 1      Y     | Savage Species 89-90
|    6th    Warblade 1      N     | Tome of Battle 20-6
|    7th    Whisperknife 1  Y     | Races of the Wild 135-9
|    8th    Yakuza 1        Y     | Oriental Adventures 55-6
|    9th    Warblade 2      Y     |

It's a lot of work for this, and it's still not awesome. Such a character must be a halfling and probably must take two flaws to meet the requirements of his prestige classes but, at level 9, has a competitive base attack bonus of +6 and weird but playable base saving throws of Fort +8, Ref +9, and Will +2. (Don't judge—a Rog9 only has a base Will save of +3.)

And, if the above character enters play as a constructed character rather than advancing through these levels organically, his backstory will be amazing.

That said, under the house rules described, this character's player'll have his choice of four rogue special abilities for his character before his character's level 10. That's a lot. Were this house rule present in a campaign in which I was participating (and were the party a reasonable collection of not-totally-optimized PCs), I would carefully consider playing a character like this.¹

However, if the players can be trusted not to game the house rule, that's cool. I mean, really, the house rule isn't so good that it automatically makes classes granting uncanny dodge tier 1 or anything, and probably won't even really affect the balance of a character with such a bizarre combination of classes vis-à-vis a straight-up highly optimized flask-throwing, Sleight of Hand-exploiting rogue. The proposed house rule may make folks think hard, though, and if that's a good thing depends upon the table.

An alternative

Instead of either getting nothing or getting a rogue special ability when a character would gain his third iteration of uncanny dodge, have the player pick a feat for his character to gain from a list of feats the DM and players develop. This alternative simply avoids the question of whether rogue special abilities, if granted early or by a class other than rogue, are unbalanced.²

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¹ That's mainly because Lady Luck hates me, so whenever I play a character that can gain a special ability that eliminates the need for me to roll dice, I take it. Having the special ability skill mastery available that early in my character's career would be so awesome for me, I might take the special ability skill mastery twice and never roll a skill check again. (Honestly, I think most players would first take the special ability crippling strike or opportunist.)
² The old school DM in me (a la the year 2000) thinks that increasing the character's trap sense by +1 upon each the third-or-later uncanny dodge iteration might be an acceptable alternative to nothing, but that also sounds sort of insulting, given that the special ability trap sense is widely considered to suck. (Forced into such a situation, I'd try to get Wis 13 so I could take the feat Dungeoneer’s Intuition (City of Splendors: Waterdeep 144); then it's almost something.)

Answer 3

I think that, generally speaking, allowing a bonus feat or some other equally powerful (subjective) ability would be a fair compromise to encourage the player to try new things. Personally, I think character planning can be detrimental to a game, so allowing characters to advance via multiclassing or prestige classes is important. I would give the character something that fit how the character was being roleplayed.

For instance, I may give the assassin the ability to re-roll a reflex save (keeping the second roll, regardless of outcome), or if I was feeling really creative, I may give the assassin something more roleplay friendly. For example, giving the character a bonus to bluff checks to aid in endeavors like talking his way past guards or throwing off pursuit might be more suitable. No matter what I choose, I would make sure the granted ability fit the character and the game.