Where to focus my ISO? More 3*? Hb?

Oshalei

I've hit a point where I feel like I've leveled all the really obvious 3* candidates. I do have a pretty well covered hulkbuster but he's 5/1/5.

Should I boost him? I see a thread here about fistbuster but with one black I don't think it applies. My iceman could come up to 152 but I don't know if that's worth the ISO when I could level a fully covered 3*.

Roster in sig.