Here is my build for a high-level and low-level defense Frost Prime:
This build requires anorikin reactor, a maxed D polarity aura, and 2 forma.I currently use a Physique aura, but I think Energy Siphon would be better. Using Energy Siphon would require a third forma.
This build is best for Infested but it can easily handle Greneer and Corpus. The point of this is to spam Avalanche in the low levels (<30-40) and then rely on Snow Globe to protect you in the higher levels (40+).
Explanation for Stretch:
I know stretch on a Frost is normally viewed as counter productive but these are 2 reasons why I think it isnt. (I copied and pasted from my comments below)
1) In the lower levels, I would be spamming Avalanche so the more enemies i can hit, the better. (I've been able to just about fill the Venera tileset comletely) I have no need to use Snow Globe on the lower levels simply because i can tank hits all day and i kill them fast anyway:P
2) Against Greneer and Corpus: At higher levels, the higher artillery comes in. The rocet launchers of the Greneer heavies pierce the Globe so the bigger the globe the more spread your team has. (Nothing more annoying than your team getting oneshot by a stray rocket)
There were 3 reasons, but the third (2nd in the comments below) was incorrect. I missunderstood the mechanics of the slow down area in the Snow Globe. That area is only the center 5 meters and is NOT affected by Stretch
Good hunting Tenno!