Reflect is a pain for sure, usually happens I usually crit myself
But with a good team and being able to balance SS-Prep firing tentacles it can be doable.
For real fun find a Reflect Damage - Illusionist - Extra Health, those are a real hoot!
The 'Illusions' do not reflect damage this is a moot point. Invuln minions, considering the randomness of encounters (IE space available), Are a much bigger problem, but faster to kill.
To the OP. Learn to pot. I personaly use elemental arrow-nether tents (EA).
Learn to time. I feed out a string of them there tenticles, and they start to hurt me, I Smoke Screen (SS)(if you arent using this you are doing it all wrong) (if you dont have this glyphed for an extra .5 secs you are doing it all wrong) in the .5 secs it takes to get another SS. In that time, I am still spamming for another SS and never stopping the feed of my EA but now watching my health ready to pot at any hint of dropping below half. I normaly get another SS off (unless its a bunched group all being luckey crited at once) and then stop the line because i wont have a pot to save me. Get some distance, start a new feed of EA, and SS just as it hits them.
The main point is that like so many others, I go in with a plan. It may not be perfect but the timing and managment of resources is key with dealing with the DH's biggest pain IMO (biggest just because time is always a factor and they force you to kill them slower or die a couple times trying to zerg it). So work it out and it becomes the norm. Feed, feed, SS, pot, feed, feed, SS, gl.
Lacuni or Soul Rippers with invulnerable minions and extra health. i don't see a worse mob possible in the game.
teleport vortex spearchuckers (obligatory extra health) have just been hilarious, disc runs out so fast trying to avoid their instant spears when they teleport or suck you in
soul rippers will always be the demon hunter bane though, find a worse mob in the game i dare you
Soul rippers with Mortar is actually quite reasonable - they have to stop to cast the mortars, giving you plenty of time to kite them (and they won't catch you with their tounge-lash unless you stand still or run back and forth when they're not casting mortars).
Personally hate reflecters the most. Bam, 300K hungering arrow pierce in my face <.<.