The new runes system makes ARAM extremely imbalanced
The new runes system makes ARAM extremely imbalanced, partially because tank runes sucks in ARAM in addition to the fact that the short ranged tanks already have disadvantages in ARAM. Another obvious reason is that abilities with multiple-waves of damages can no longer trigger "Electrocute" (the old thunderlord): for example, Garen's E. With the old thunderlord, although Garen is short-ranged and has no gap closer, but can do fetal damage once land his QE on a enemy. But now, Garen can no longer trigger "Electrocute" with QE, and this funny champion became useless (even with tank build, because he has 0 CC).
After playing 50 ARAM games with the new runes system, I can confidently tell the results after seeing two team's champions. This mode became so boring because everything depends on the champions, not skills and play.
ARAM has never been a balanced game, however, it definitely became much more imbalanced after launching the new runes system. I really wish Riot could make some efforts to change that.