I don't understand the "too much true damage" argument, because I don't think getting IE on Trynd is a good buy on him at all. IE doubles his crit chance, and Trynd usually wants multiple crit items (shiv and pd is a decent combo) for their passives and AS along with crit so he can split push with impunity. IE is too expensive and only gives raw AD, which is only part of what Trynd wants. A usual build for Trynd would go for AD/AS/CDR items so he can hit the cap early and spin to stick on targets, similar to AP but having a much later power-spike.
Complaining that Conqueror gives too much true damage is a completely valid statement, however. That being said, that's not necessarily addressing why Tryndamere - the champion - is an issue.
I don't think Tryndamere is in a healthy state, even though I enjoy playing him, although I don't want his identity as the unkillable Barbarian to be tossed out.
I wonder if his passive disabled crit chance and instead allowed him to get a guaranteed crit every x hits and the number of hits scaling 3 times (6, 11, and 16), might be better - something similar to Samuro from HotS. You would have no threat of early cheese kills while knowing when you need to play around his crit.