1) I already know that, but that wasn't said. Of course it dies pretty fast now IF you damage the engine but the last time I played a guy that used SU85 and wasn't able to slow me down I took about 30% damage before blitzing behind them and killing pretty fast.
2) Not true at all. Having more available of options in a genre that is based around choice making is an advantage. Not only that, but even if said P2W unit is able to be killed, it is still unfair if using it requires less skill than killing it. I'm not saying that is the case this patch, but saying "you can beat it" as a broad justification for any DLC commanders is flat out incorrect.
Are we talking about all DLC? Because this argument seems to be focused more around the Tiger Ace, which from what I've seen in the higher level games that I've watched over the last few weeks, has actually been more of a hindrance with the massive resource drain it causes (Edit: At least in 1v1/2v2's). Which means that if you can dance around the Tiger, harassing points and trading on MP the opponent is going to be able to keep up with the MP drain.
As for other Commanders that provide a significant "I bought this and win" advantage", no others have been brought to my attention.