im using in AI fights just my 3 most favorite characters, nothing more and only do those 5 fights per day for Augments, Skins, Gear, which you can get proly only in there. and if i cant beat something in Towers of Time, AI fights can help.

I use it if I need to make dinner or something but want to play a tower set before it expires.

The AI isn't smart enough to stay away from certain modifiers and almost never makes enough points to get currency bonuses, so most of the time I just play it myself. Sometimes I'll use it against the end bosses in a tower set just to save time -- the computer does usually make those bonuses and it's more efficient if I don't lose a couple of times doing it myself.