There are so many issues I have with the Sisters and new Lich mechanics.

[(XBOX)TehChubbyDugan]

First off, one of the big complaints, which was that once you knew mod order you ended up running seemingly endless amounts of missions that were completely pointless waiting for your lich to spawn in so you could finish it.  It seemed like the addition of the RJ mission was to remedy this, and instead the issue is still 100% there and now there's just an extra step to this already layered grind.  I just ran enough missions to finish off most of my requiems after I had already learned all 3 mods, just trying to get the damn thing to spawn.  Now instead of being done I have to go run RJ.

Even after learning the mods and finally getting it to spawn in the misery didn't end because it practically sprinted for extraction and then stayed there so I couldn't go after it without bailing on the mission and leaving it behind.  I managed to coax it out after a very drawn out engagement.  How this is something you allowed to happen mechanically I don't understand.

The sisters also feel like more tank meta enforcement, because you can't play evasively with their shield regen set that high and with that much DR on them.  You have to stay in their face and they put out enough damage even at level 3 to just straight blow though Warding Halo in a handful of seconds, no matter how high it gets.  It's fine in absolute meta setups, but the damage output is just as absurd as the rest of the corpus faction, but they have all the durability of the heaviest Grineer.  

[notSeth]

How about my Rhino, whose Iron Skin doesn't even last a full actual second before being obliterated along with my shields?

Yeahh, they deal too much damage and are too tanky, but it's kinda impossible to make them a challenge without changing the base game mechanics. At this point, Revenant is my go-to for these kinds of struggles, because he can reliably do lazy CC (even to liches/sisters) and can tank attacks of any amount of damage. In a sense, it's perpetuating the same kind of cheese that gets us into these kinds of messes.