They use to have it ( I think anyways, been a while )
And it is not that I do not think they are not hard or challenging, but I view them more as end game for something to do. Both are very much intended to test and push your roster, give you a reason to continue to play, and improve your characters. If they did not, people would just quit once they maxed out.
In time, I hope they will address GW to where skills are factored into the power rating, that should solve a lot of the problem that many hit.
TB, is new, the later phases are tuned for G12 gear, and specificly made teams. As well as having a large roster to fill all the CM teams, SM teams, and Platoons. Sure it is going to be hard atm, it has not been out for more then two months yet. If it was a breeze, then again, people would not have a reason to upgrade or keep farming things.