I, personally, love the One For All mode, and I love URF (maybe you could combine them sometime and have an OFA-URF game mode?--side tracked). I recently played a game as Vlad against Tahm Kench. There is no counter-play to the frog. Their stuns last forever, they can continuously devour you, over and over and over, and if you're devoured, the next Tahm Kench picks up the Tahm that has devoured you and drags you out (with his passive speed _BUFF_ and throws you into the middle of the other Tahms who just rip you apart.
There are two solutions to this problem that I see for One For All:
1) Reduce how long each passive stack stays on the enemy champion. For example 2 seconds instead of the full 7 seconds. That would reduce the stun/devour duration and give some, much needed, counter-play. Allowing, ie. a Vlad to pool, drop his stacks, and be able to use his combo, instead of being instantly devoured by Tahm.
2) I know that it must be fun for a Tahm Kench to devour a Tahm Kench who's devoured an enemy champion, however, the speed buff that the second Tahm gets defeats the purpose of him being slowed with an enemy champion. If there's a way to add to the game a check system to see if the any of the Tahms that have been devoured have an enemy champion and then apply the speed debuff, that would be great.