What's the point of giving controller's control effects...

If raid bosses are immune to them regardless how high a controller's dominance is?

I think a debuff is technically a cc as you are controlling him making him weaker.

I mean things like electrified stuns, sticky bomb juggles/dazing, hard light panic, encasement etc etc.

Well with bosses that can summon adds it makes more sense to keep those in check instead of the boss. Stun, juggle, daze, encase them and such. Really all that is needed to be used on a boss is debuffs.

This. Crowd Control is for the adds.

If you could cc any boss, that then trivializes the boss. What makes the bosses hard is that they do their thing and we have to react. Unless the scripted reaction is cc, then no cc should be used.

if you could cc bosses, you would break the game and make content laughable.

prime battleground with the old orbital strikes as an example

I understand why our CCs don't work on various bosses and even some mobs but I'm having problems understanding why our stuns and debuffs are missing from time to time altogether.

Agreed. That's why they call it CROWD control, not boss control.

I think this is the best answer. fir the same reason they nerfed the cc on the orbital strike. before the nerf people went through prime like nothing when the mainframe items came out and took out the challenge of the raids. also for the same reason why In every other game the bosses are immune to just about everything cause their suppose to be super tough. like someone said though they do spawn adds and those adds are not immune to cc effects sui that's why it's good to keep them.