I think its more a case of, the more you play the game the more you realise (or read up on) what works.
My first toon Develle absolutely sucked back in CoH beta, as time went on she became more refined and more effective.
Still another aspect is the continuing nerfs, sorry difersification of powers. To do the role that has come to be expected of the tank (i.e not die and take the agro off the team) the focus on what powers you need to do the job has become more and more narrow.
Certainly before you could have a far from optimum build and still perform the role, now tanks have to be very very specialised to fulfill their duty to any kind of effectivness due to their expected nature of them being the first one into the firing line.
yeah back in the halcyon Days of I3 you could get to teh des cap with just the passives and Unyealding, so everything else form the set was a bonus, so it allowed the taking of other powers from the pools, which ment a more rounded Char, now you need all of the powers just to geta decent amount of Res from anything, and the passives are less and less worth it, its a sad state of affairs 
don't get me wrong, things did need to change, i jsut think they were too drastic, instead of weeding they razed the whole thing.
Hello, I have being doing some thinking alot at the momment with my tanker now my first hero was brick000 and i didnt realy no much about what each archi was and the best SO's. It had taken about 4 respecs in tottal to perect my tanker..but the thing i have beggan to notice is the lack off varie in them..such as needing stamina, needing unyield etc.