Something similar happens with the 2nd Boss in Saalus Canyon Area, itâs that damn âmini-vacuumâ skill that interrupts you and cancel your skills animation/damage (but still puts the skill on CD), very annoying indeed. 
Anyway, I understand everyones concern about Pain Barrier and possible competition when the new World Boss system will hit iTOS, but honestly Iâm not really surprised, and PB is not really the main issue here but just the tip of the iceberg.
I always had two Boss killers on my account, a Fletcher/Mergen (my main) and a Doppel, and even way before the balance patch hit, I often used the Doppel for Boss killing given the right conditions (even tho my Mergen has always been better geared) and itâs simply because of one very important thing: party buffs/debuffs.
A Doppel (or any other physical damage dealer) becomes a real monster with the right party setup (for some buffs/debuffs you donât even need to stay in the same party) and itâs always been like this, even before balance patch and the knock-back spam from Bosses.
Dragoonâs Serpentine, Taoâs Storm, Mikoâs Kagura are all huge buffs that together give your physical DPS a HUGE boost that is not easly surpassed by other characters⌠the scaling factor is simply that much.
Before the balance patch and the nerf to monstersâ health pool, if you wanted to do Blut/Nuale whitout taking ages (or involve many players) that setup was the way to go, I assume it wonât be different this time around either⌠pain barrier or not, the synergy between ranks is more or less the same itâs always been since rank 8 came out, it just became more clear whoâs better fit for the job now (sadly, some ranks seems to be fit for everything nowadays
)