Amne does so heavily depend on the ST/ability design that it's very hard to say if it needs a buff or not. Allowing it to guess while dead is probably the most common house rule, and it makes sense, more 'feelsgood', but it also changes the dynamic of the character - without it, Amne becomes a "I need to survive at all costs" character, which is fine if you don't have a dozen of those on script (or run all amne games).
As for the abilities, ideally you want something with either prompted player input (narrowing down guesses), a minimum floor (so that it helps town while alive, even if they fail to guess and/or die early), or visible gamestate effects (otherwise impossible happenings that either prove its existence, or may be attributed to it and thus allow for better guesses, again). If it's not within those bounds, you better have additional things to help them (like setup abilities including "you start knowing you have a setup ability").
Allowing Amne to guess while dead does removes a portion of the hide&seek of a valuable amne ability that may want to stay alive for longer to pinpoint their exact effect - which in turn makes setup/early game abilities more powerful, because then you can die and lose nothing, since you can still work on solving your little minigame within the game. And that's a bit of a shame. And yes, sometimes an each night* amne dies early, and it's a bit of a shame - but that's the same of many continuous info roles, and not knowing whether what exactly your ability contributed to the overall puzzle is also part of why it can get away with powerful abilities overall, as a tradeoff.
So, eh, I'm kinda ambivalent towards the house rule. I prefer to play without it (outside of all amne), and instead design abilities that don't run headfirst into that problem overall.