Here's what I was thinking. Bombers' choice of armor is terrible because all four sets are only elemental and normal. So I was thinking: would it be better to use other gear plus bomber trinkets or just use bomber armor? Like, when I want to fight Royal Jelly with bombs:
Setup 1: Deadly Virulisk set + 2x Elite Bomb Focus Modules. Result: piercing and normal defense, very high damage bonus vs. slimes, and maximum bomb CTR.
Setup 2: Mad Bomber set + Elite Boom Module and another random trinket. Result: elemental and normal defense, maximum bomb damage bonus, and maximum bomb CTR.
Defences, once your skill is appropriate, does not matter much since one can dodge enough hits to stay alive.
First set sounds pretty good, to be frank. Good defences, and enough bonus damage to use ctr trinkets. 2nd set, in comparison, takes much more damage for a med boost in damage. I think virulisk is 5*? If it is, then the 2nd loadout seems to be cheaper, saving energy on crafting an extra trinket. Might be a bonus, might not be.
Keep in mind that these are for a bomber who plans to deal damage. You could conceivably go with skolver/azure/other piercing defence sets and use bomb focus trinkets to still achieve max ctr.