I don't like liches because at the end of the day, you're doing the same old boring missions you've done a thousand times, with the occasional "Press X to kill a thing" added in. And no, having lvl 110 enemies doesn't qualify as making the missions challenging or whatever. There are plenty of frames that either lock down the map or kill it before it can spawn.
The missions themselves are just lazy, basically just crank the enemy level up and spawn a thrall or 10. That's the only connection they have with the liches, When we do a mobile defense, we're not stealing lich data that adds to our murmurs, when we're doing exterminate we're not facing a higher than normal number of thralls, it's all just the same thing. The lich fights themselves are boring too, basically just a little tankier versions of normal mobs with wow, resistances? Yeah Mesa exists and she doesn't care about any of that, she just looks at them and they die.
At the very least if we could farm fissures or something while farming murmurs, it would at least feel rewarding.
Also no, it's not a nice helper, it's a waste of space that does nothing to enemies but tickle them.
Where gas and slash liches DE?
Don't even get me started on the 5 forma requirement on the kuva weapons. At least the saving grace of that is that you can slap whatever mods you on want them.
I forgot this scenario: You run lich missions, you're a few murmurs away from knowing the 3rd requiem. You get the last murmur and hurry to the exit then boom, your lich spawns. Since you didn't know the last requiem, you fail to kill it and now you're forced to run lich missions for no payout for another bloody half an hour until it decides to show up again.