Well for starters the tag mechanic isn't meant to be just some sort of gimmick that they just throw in for the hell of it or that it's the new cool trend to have assists and tag gameplay or anything like that, rather they built the game around these concepts and again they're likely only doing this 1v1 stuff because when it comes down to it casuals are going to look at it and say to themselves "how many modes does this game have" or "how many options do I have when playing".
I'm pretty sure we're all well aware of that...
...and will have no effect whatsoever on competitive or serious players.
It depends. In terms of balance, if the rage boost affects a character who is already considered ridiculously strong, then yeah of course someone's gonna blow the whistle on that and say something, and that in turn may affect how tourneys run this game...
Also it really annoys me when people say that they should just bring back everyone completely disregarding any possible issues involving balance, time, money the fact that a lot of people already complain that there are too many characters as is and at the end of the day it just doesn't add up.
Well, for starters, people have been crying about Eddy and Christie being separate characters, and it happened... People wanted classic Jin style to return, and Devil Jin was truly born... There's only about 5 characters missing from the Tekken universe; I'm sure there's no big issue in adding them in... And 40 characters in a 3d fighting game isn't a big, when in SC3 you had damn near 40+ when you count special guest characters... If they were to make another one several years down the road and add all the characters in the SC universe, it would definitely go past 40...
2D fighting fans are always crying for more characters (*cough* *cough* MVC3OMG *cough*)... Sure, it's a 2D game, but compare the balance of that game vs T6... Compare the balancing of the first MvC3 and T6-- T6 had more characters at that point, and was more balanced than MvC3 was... 2D vs 3D doesn't matter at this point either...