I've just crafted a suit, with High freeze resist.
What would be a good helm with it, other than Hiss(which I own as 3*, already making me near invulnable to freeze).
Should I get Volcanic, in order to have both fire and freeze?
What is the chances to get UVs with a Bomber helm? Especically fire?
May i ask, is a Volcanic/Bombastic combo good?
Even with a Fire High?
Have you read the Bombing Guide on the wiki? I goes into some detail on the bomber armor, including the combination of Volcanic/Bombastic. Edit: Sorry, itr doesn't do this specific combination (anymore?).
Offensively, you're just choosing your mix of damage bonus and CTR. The ideal choice depends on which bombs you're using. All bombs benefit from CTR. Damage-oriented bombs also benefit from damage bonus. Other bombs don't benefit from damage bonus much; damage bonus doesn't improve the shock of your Voltaic Tempest or the duration of your Graviton Vortex.
Defensively, you're choosing whether to protect against fire or freeze (or shock, or nothing). The ideal choice depends on which monsters you're facing, as I've already explained.
In short, you haven't given us enough information to determine the best choice for you. If you just want a simple recommendation, then get double Volcanic Demo. The CTR is useful on all bombs, and the fire protection is useful in FSC.
Mist.
However I need something that is an heavy hitter.
I wield either a calibur or a Blizzbrand as a side weapon.
Ie, there is no documentations on Vol/Bomb, noor kat combos.
Getting medium damage does make a difference in the amount of bombs required to kill something, particularly in larger parties, I can tell you that much from experience. A medium CTR/Damage combo would probably work out pretty nicely, but I'd have to do a bunch of tests on as to whether or not it'd outdamage full Volcanic.
For the chances of UVs, read the wiki page "Unique variant".
As for which defense you should pursue, it depends on which enemies you'll be fighting. The most popular destination in the Clockworks is Firestorm Citadel, where fire protection is great and freeze protection is useless. But most bombers decide on their gear based on the offensive bonuses, not the defense.