Until next patch where they'll probably change it so you can use weapon skills and not lose the stacks.
I am pretty sure that's going to happen.
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If they decide to add it back, keep the animation locked... So we can ride monsters head and allow us to go into a QTE(Quick Timed Event) where we stab multiple times.
Watch them bring back Assassinate for a new Job in 7.0 because they want that job's mechanic to focus on Assassination.
I honestly can see SE do that as they did that with certain old mechanics of currenmt jobs that was removed from them now. We have a few examples already such as certain Dark Knight's old skills they removed from Dark Knight been moved to mechanics for Reaper job.
I also had a guess for a long time that the 2nd Scouting armor job maybe a Job focused on Assassination mechanics since 2.X when Rogue/Ninja was just released if SE never expanded on Assassinate for Ninja and began focusing more on their Ninjutsu instead which did ended up being the case in the end as now Ninja is 100% focus on Ninjutsu.