Universal damage is more valuable because you can't rely on UVs to acquire it. This mindset works better for swords and guns... but bombs it gets a bit iffy. Bombs are incredibly dependent on CTR and it really should be your main priority.
Also with the current Radiant shortage, getting a lvl 10 5* bomb is not as straight-forward anymore.
@Narfle: Yah i guess using mix of mad and bombastic to get max in CTR, Why no Chaos ? cuz "i know" is going to get nerfed hard again or they are going to buff mad.
@Traeve: Yah i know that, all my weapons are rank 4 exept the opecrea one.
I know Chaos and Mad are going to get balanced, too. I even knew it back when they got unbalanced nine months ago.
But until that balancing happens sometime in 2089, I would suggest you craft Chaos.
Bombastic by itself isn't going to help you if you're having trouble with devilites and slags--still gives you no native shadow def, and you're left using your sprite perk on bonuses you would have already had if you had stuck with either chaos or mad bomber. I highly recommend working on a 5* Kat Hiss instead.
"cuz universal damage UV is a lot more valuable than CTR" --> No, it's really not. Getting off more bombs by maxing your CTR will increase your damage output waaaaaaay more a lower CTR + dmg bonus. And besides, bombastic isn't universal; it's bomb-only, just like mad bomber.