I wanted to make a 300pt theme-team composed entirely of figs rated as 5-star on the HCRealms units page, I ended up choosing scientist as the keyword but am open to other keywords

Here's 3-versions of the team I made (same figs but different feats)

AV Spider-Man 111pts
+Stunning Blow 10pts
+Armor Piercing 10pts
SI Mr. Fantastic 100pts
MnM Dark Beast 69pts

or

AV Spider-Man 111pts
+Stunning Blow 10pts
+Lunge 5pts
SI Mr. Fantastic 100pts
MnM Dark Beast 69pts
+Lunge 5pts

or

AV Spider-Man 111pts
SI Mr. Fantastic 100pts
+Brilliant Tactician 20pts
MnM Dark Beast 69pts

thoughts?

Well. If you're going off that criteria. I'd go for the gold. Or in this case Red and Gold:

Build
188/ SI021 Iron Man
111/ AV051 Spider-Man

299

yeah I guess that would work

Spider-Man Holds them down.
Iron Man shoots them down.

And use Alpha Flight to bump the attack value if you think they need it.

I'd go with Mr. Fantastic+BT, Dark Beast and Iron Spider (-Man).

SI Iron Man is great, but with only two characters on your team in a 300-point game, you might be out-manuevered or -actioned by a min/max, or demolished by a tentpole team. The advantage of using IM is the ability to carry Spidey, but web-head will always have to be given an action to attack or move first. You'll have to always rely on Tony's Perplex and Outwit, leaving him more vulnerable to an attack (the use of Outwit eliminates his use of Super Senses).

Dark Beast will always need to be adjacent to an opposing character to wreak havoc, but he'll definitely soften up the target for Spidey or Fantastic to finish off. Besides, he has one of best special powers in the game: the ability to Incap or deal damage without making an attack roll.