not as good as you think. sure it sounds like a wonderful idea on paper.
but on reality, DN L is bad. really bad one. it will be better to put Zaal+Mission in other team, and use Sith with a proper L.
this sounds cool, but can be easily dealt with, and the HP replacing protection is simply often hurt the team and make it much more vulnerable. so not only that DN L is much worse than many other L you can use, but it can also hurt you and make your team "easy" vs the proper enemies.
Example will be that you use 5 people, including DN, Vader and Zaalbar (3 huge toons). i bet i can use Zader L, MIssion+Zaal and Sidious, and win this team 4v5, when using 3 toons that you use, and not even DN (which is again, huge, and needed as counter for revan). the DoTs will eat that DN L team, also exposes, plague, chewie, and such. bringing Savage for example as 5th for my Zader team would make it even easier, since he can overpower pretty fast. i think this is saying a lot.
the fact that i can use 3 of your toons + 1 that is WEAKER than DN, and still win you easily, shows how much lack of synergy that team have, although the idea of perma-taunt sounds cool.