Usage of たか at the end of the sentence

Question

今日じっくり観察できる分 殺しやすいこと分かってきたっぽい

To which the other character replies

そういうこと無駄に学習能力たか。。。

I understand he's saying it "that is useless knowledge" but what does たか here mean? More so, how does 無駄に work without a verb? Wouldn't 無駄な make more sense?

Answer 1

That たか is 高い said with an exclamatory tone. Dropping い at the end of a sentence is a way of expressing the speaker's surprise or amazement. This question is related: In real life, do Japanese speakers exclaim things like 熱っ！ or 痛たた… or 寒！?

無駄に is in the adverbial form because it modifies an adjective (an adverb can modify not only a verb but also an adjective). Note that the subject of this sentence is 学習能力, while そういうとこ serves as a broader topic.

そういうとこ(は)
As for that / When it comes to that kind of thing

無駄に学習能力(が)たか…
your learning skill is unnecessarily high...