This is just how I'm looking to build the coolest frame in the game for defensive mission types. Once I've fed him a few more Formas, watch this space to see if I regret my choices.
Snowglobe does snowglobe things, while Avalanche is specced to strip 100% armor by base over a large area, giving you every opportunity to make as many awful ice puns as you can as you rip your enemies to little frozen chunks with impunity. Ice puns give Snowglobe an armor buff, I swear.
I've chosen to infuse Pull over Freeze here, to work with Greedy Pull and Arcane Energize, to supply energy to the whole team if they're near enough, and that's often the case in mostly-stationary objective-based missions.
Arcane Pulse might seem like a bit of a weird choice here, but it follows the same logic as Energize for a bit of radial healing. You'll be swimming in orbs from the massive Pulls, so why not slap [Synth Fiber] on your sentinel and give Trinity another excuse to go to Rework Therapy? If you're babysitting a cryopod alongside any kind of push-button-to-win build, they'll appreciate you keeping them alive, and keeping their nuke button looking all nice and shiny as they spam to their heart's content.