Gaah! I hate these guys! It’s almost enough to make me a DC guy. Three I can handle. But waves of them…!
Give me ninjas. Give me Mindless Ones. Give me Maggia. GIVE ME ANYTHING BUT WAVES OF SENTRIES.
I agree. I found medusa, kamala 5/3/5 and 3* Hawkeye make a great team. Two healers firing off constantly. That might be my new go to team for other events.
On the Sentry/side nodes I was doing the same, using the required toon plus Medusa & Hawkguy. This event was profitable (hit full progression, personal and alliance) but sort of boring as I was using the same two teams all the time. Gambit, IMHB, and America for Ultron, and Medusa & Hawkguy + required for the side nodes. But it was working, and working well, so it didn’t make any sense to change it up 
Hawkguy and Bulls3ye have become my go-to duo against waves of sentries after the most recent Ultron event. Medusa, as in many cases, makes a good third for this team.
Set Hawkguy’s black at five and you’ll get two blue and two purple AP each time you match one of the many enemy specials. Let Bulls3ye use the purple AP to eliminate the hard-to-reach enemy specials and his black passive will load the board with friendly strikes. Medusa’s attack tiles double dipping all those strikes will make short work of even high level sentries.
It’s fun to have a couple of 3*s so well-suited to taking out such annoying enemies.