I'm high and don't know if this will help or anything, but a VHS/4k solo MMR player chiming in. I play almost only unranked, played solo placement and stopped after that. Score in placement was 4-6 w/l, I believe.

Undying has died down in picks (purely EUW with maybe one exception a week) after the additional patches on 6.84 almost to a halt after the initial burst. My friends and I have been running a ganking support or two of which one has been in many cases Sven. Due to his mobility and stun he is extremely strong as a support that goes for example treads-->blink and roams like a beast, finding some farm in an empty lane or the jungle when possible.

We've run several different line-ups (none really thought out except for the Sven and another stun roam combo). We try to keep a balance in squishiness even though we mostly steamroll early and snowball and build somewhat tanky on carries in the mid-game to survive any potential burst that a level 11 Lina can dish, among others.

Matchmaking has also been weird, maintaining our approximate winrates and not having any massive dips in unranked MMR, we've still been in high skill games (not very high skill) which has been (not to sound cocky) below our skill. I don't know if I should blame matchmaking or what but we've been lacking a challenge in some games.

Also, in games where we lacked the proper stun support combo, we did struggle to some degree. My Phoenix game for example we struggled early but were able to comeback when I all of a sudden got 2k gold after a teamfight and decided to go radiance. The radiance then allowed me to farm a quick shivas whilst the rest of the team tried to buy time, me joining them pretty much exclusively for teamfights, otherwise kinda avoiding the enemies.

If anyone has any questions or thinks my post is shit, let me know.

Ps. I hope this was coherent.