I use K2S0 quite a bit, and he works well with Cassian, but I don't know how good he'd be with your lineup.
I personally like the taunt mechanic, but since the taunt goes away the moment he takes damage, you have to be conscious of that and decide for yourself if that's what you want out of your tank. He counters a lot, and most of the time, those counters put the taunt back on though.
If you use him, make sure you put plenty of tenacity on him, because when he's debuffed, his counter chance is cut in half.
Scarif Rebel Pathfinder might be the better tank. His health, protection, and armour are all better, his basic gives TM, he has a more traditional taunt (that comes with AoE damage and debuffs), and he revives if he dies with any buffs. He's a cantina farm, so that's a bit of a conflict for you, but you can get him in the Fleet store as well, but then you're at the mercy of the cycle.