I’m not sure a UI element defines the interactivity of the mechanic.
The fundamental issue with your assertion of “even a split second of CC can interrupt a boss’s special moves,” while true, is predicated on players being able to get that split second of CC. The earlier portion of your comment seems to indicate that it’s your design that they be able to (“Most bosses are not completely immune either”) but that simply isn’t the case.
You’re right, the DBM warning that pops up is.
For the record: Faction Champions were cc’able. 
And there are bosses (Reliquary of Souls e. g. iirc) which are hard without interrupts frm Rogues.
I played years back in the days and still don’t remember many details like CC or champion or such. Oh, Un Goro though! We need that kind of zone with dinosaurs and volcanos and such 
What was the topic? CC, maybe GD 2?
Hehe, well, I really like CC. I like positioning and I liked my Rogue with Kidney Shot and Backstab.
But is it really necessary here?
Necessary? No. GD has sold millions and it’s been released for years with new players arriving daily.
But some (like myself) would argue it’d make it a hell of a lot better.
Edit: As it happens, the converse to this argument is that I’m far-more against players being CC’d than I am a proponent of players being able to CC bosses. It’s quite the sidetrack, but it’s my biggest gripe with GD, games like Monster Hunter, and any other PvE-centric system…
Dragon age, your Rogue play style literally is based on backstabs. And there Rogue avoids damage by CC ing enemies. And you need this kind of stuns since you have low armor and health. But you know CC in Dragon Age don’t work on dragons and bosses in general. Complete mystery why 
I played all these games (hell, I am a lot older than you 
), but…different games.
Here (in GD), CC in my opinion works. Heroes, etc. and I use “tactics” on them. If a boss spawns adds…very effective. Sure, cc on bosses would bring something new to the gameplay…on the other hand, bosses have to be made harder, because of these new possibilities. And perhaps CC is the new Meta or even mandatory for some bosses.
CCing bosses in GD with a duration of a fraction of a second would effectively be an interrupt. It’s giving the same CC skill at least some use vs. it feeling bad to use because it loses its effect completely.
It WoW it even seems more severe, because the boss spends more time casting a spell which just gets interrupted. It was effectively CC’d while casting.
Honestly, asking for longer CC durations on GD bosses than just a short moment is too much, in the current state of balance. Unless any source of damage would cancel the CC.
How about this, no cc but maybe add a sort of roll/evade skill to your character?
all this talk about cc on bosses makes me want to build an end tier char focusing heavily on cc like off/blade trap, just for focus farming on mobs to farm their crafting materials and MIs. maybe its gonna be not really faster than cc-less builds for that job. but at least it will have unique gameplay styles and roles (a gatherer of materials from chthonic beings, for example).
Someone’s gotta keep the merchs of Cairn stocked.
It’s called medal augments
Freeze has some practical use on Mageslayer. Debuffs from hero mobs are pretty dangerous. Example: in Crucible 162 on a non-toptier you wanna clear the mobs somewhat (especially Timewarped and disrupters) before you engage in MQ facetanking. On Mageslayer you can go directly - and if not kill her first at least apply your DoTs - as OFF keeps you mostly clear of debuffs till they thaw.
But it is true that at 160, 169 and 170 you can forget you even had OFF unless that Unchained (or sth, correct me) mutator giving penalties to enemy cc res.
Question: if you (somehow)freeze Grava during his nullball animation, nullballs won’t come out but the skill goes on cooldown?
Didn’t use them yet, do they provide an invencibility window?
No…that would be absolutely broken.
EDIT: But you can become untargetable by most attacks if you use a rune with mechanics similar to shadow strike.
^If IIRC, yes. It’s similar to how mobility runes go on CD if you get CC’d during the cast animation. But I may be wrong here.
I’m sure that simply removing the cc from item skills (Mostly talking about proc skills, which are shared between most items), removing %cc chance from rare affixes (Still few), then finally cleaning up devotion procs (Confuse on Imp, Petrify on korvaak, Freeze on Ice Storm, etc.) will make the chances of chain-stuns happening nearly nil. Finally, pushing most of the duration of CC mastery skills to the ultimate levels is the ultimate way of (pardon the pun) controlling their efficiency.
It isn’t THAT hard to do. (Less than a day)
And yes, I’m very much for making interrupts or temporary CCs work on boss. One way to make it more interesting is having bosses cast an “anti-CC pneumatic burst” with an example of a 6s duration, 10s recharge, and a very visible effect (aura, cloud, purple glow). While the buff is up, CCs pretty much don’t work. But while it’s down? Go to town.
And no, having the CC options be limited to Rimetongue and Mageslayers full builds is just bad.
So is OFF not being able to pick up trash like Aether Crystal formations.
The idea of bringing this up was because the game is going to change a bit on the next patch, and maybe there is a small chance that this kind of feedback would be taken into consideration, at least as an experimental idea.
Wild idea: make the bosses have a “CC bar” that starts empty and fills up the more you CC them, when the CC bar fills up, you can’t CC them until it depletes again.
Having a buff that protects against CC, with a downtime, accomplishes exactly that. Just without a fancy UI element.
Yes, but the bar would help the player to know the timings.
