ADCs are out of order in ARURF - likely done with the mode.
I had a lot of fun with the mode but people have caught on to what works best and ADCs are the win condition. If you don't have them you lose. If you have more than the other team, you win. You have about 15-20 minutes to end against an ADC before it's over. At that point they start to transition into level 18+ health scaling. Allow me to explain. So you'll have an ADC with some lifesteal and some assortment of stacked IE, etc. In other words, 6 glass-cannon items and they'll have 3300-3800 Base HP. But that in itself really isn't the problem. Because of the ARURF crit buffs and such, it gives them a MASSIVE pool of health with which to heal back and plenty of survivability to sustain it. Meaning, in effect, they can sit there and facetank anything and right-click and then go next. Also, they get to build auto-attack centric but of course that AD scales their abilities in most cases. Everyone else has weak auto-attacks. So they're able to double-scale and their abilities carry them through their weaker (but not remotely weak) early game where they will catapult to hypercarry status. What could alleviate this is if they were bad early, but they're almost always getting fed in the first few minutes.
The most absolutely ridiculous thing, frankly, is that in an 80% CDR mode, the auto-attackers are STILL outperforming the ability-based champions. Just take stock of that and let it settle in real quick. In a mode with 1-2 second cooldowns, it's still "better (or more) ADCs win."
It's not supposed to be a balanced or competitive mode, I get that. But ADCs are waaaaaaaaaay out of order; hopefully Riot takes note of it for the next patch or the next iteration.