Speaking as someone that mainly plays support in FSC:
If you're fighting Trojans as a support bomber, you're doing it wrong. Use status hazes besides freeze such as venom veiler or voltaic tempest to create opportunities for your teammates or make them more effective. Shard bombs will give you a large area of damage to add to your teammates', if a little unwieldy. Dread briar barrage (the 5* version of the snarbolax reward token bomb) is a personal favorite as a "sidebomb", though a sword or gun is usually good to carry with it thanks to the oilers and puppies.
Also, Polaris is the worst possible weapon to use with shiv. No close range effectiveness (where a bomber is weak), weak damage per shot to use on a frozen target, and the shock can break your freeze. Not to mention it's an annoying as crap gun.
If you must only use 2 weapons, use a sword with shiv. Brandish lines will be easy to use and spamming their charge will help you with short to medium range threats. If you MUST fight Trojans, blitz needle is the obvious companion. However, if you do use blitz I would strongly suggest investing in a third weapon slot and bringing a sword as well, because blitz essentially has the same weakness in terms of usability as bombs.
Metagame says blitz....
Bombers say DBB/shards...
Swordies would tell you to pick up a rapier of some fashion...
Gunners would laugh.
You should consider becoming a shadow defender if you wanna play a support role... I hear they're awesome for support and stuff.
Anyway, I'm gonna say that for a supportive role, consider using Plague Needle, Sudaruska, Scintillating Sun Shards, Nitronome (sometimes simple blue-screen of death is best case), Furious Flamberge (trojans do light), or Fearless Rigadoon.