does anyone know if items that grant +% chance to deflect projectiles works in conjunction with colossus' skill: deflective armor?

for instance, does wearing repulsor field artifact work with that skill?

No. Two Different Things.

However if you read tool tip on Deflective Armor it has a higher chance to Proc when your in your Guardian Stance.

Yes I saw that, but I usually solo so I don't really use that skill.

So u just let bosses slam ya ?

Must be low level then I assume?

32 currently. I usually just osmium punch / spinning fist them while spamming med packs.

Maybe I'm just not seeing how useful that skill is or how to use it.

every boss has a attack animation that you see is coming giving you a small chance to block the damage making it possible for you to not have to take alot if any damage from it, that way you can kill them but if u just fight and not block anything you will have to do what you do and spam med packs and waste your credits on those instead of more important things in the game.

This. Also because of the extra chance to project projectiles from your Guardian Stance you can avoid things such as the rocks that shocker brings down from ceilings and other animations that bosses have.