Dominator, Margaret, or Iceblink

Which should I get? They all seem to be top tier in their respective roles (tank, dps, and cc) but the rub is that I can grab one using the altar stones from melting low star heroes down. I can grab either dominator right now, Margaret in a week or so, or iceblink in a couple weeks since they're 2, 3, and 4k stones respectively. I'm currently running 4* Tanner as my main tank, 5* deathsworn in slot 2, then 5* starlight, 4* aleria, 5* faceless, and 4* Norma. I could also 5* aleria in a few days if I get enough of those lava-lookin ranger dudes.

Best to wait and for Marg or ice or grab dominator right now?

Edit: I could also grab bleecker for 2k or Walter for 4k