Despite maining Thunder, I barely was able to beat T3. Well, barely is probably an overstatement since nobody died and I just autoed the first wave, but all five were almost dead by the end of the run. Like, sub-1000 HP dead. Luck helped.

I didn't try it, but I am pretty sure T4 is entirely out of the question without heals. I guess that means looking at Sol when Miracle Ticket hits us...