The burning effect in URF death match and prize fight favours mages too much.
This burn effect is meant to encourage everyone to fight, and it does work. But in urf a melee champ cant just dive into the enemy team without being instantly blown up, so whats the point? They either die by burning or suicide. Mages (and some adc's) have a far greater advantage because they can safely poke and retreat which stops the burning. It gets really annoying in prize fight when a mage can literally hit a melee champ once, then run away for the rest of the match and the burn will finish them off. Mages with long range CC are especially good like lux or ahri.
Note that this doesnt apply to some melee champs, there are some assasins/bruizers with a lot of mobility and burst who can overcome this but for most melee champs its just too difficult.
Maybe the burn damage could be reduced or even removed, its just not fun to deal with.