Don't shred the bots, only shred Malak. Get the first drain triggered, lower the Crit immunity jedi's hp so that he drains that one. Then kill the rest jedis, kill bots but only after you get stack of shred in. You want to have 2 bots up when Zaalbar has shred ready. Avoid Malak completely untill 5 shred stacks. Then kill Malak.
Crit immunity is they key for Malak encounter. Give him the buff so you cannot get feared (you cannot crit Malak), then you can aoe as much you want (obviously not too much so that Malak doesn't get to drainlife any of the other Jedi's).