Its not the "everyone builds health" thing thats getting silly, its that when you end up against a team that has a regular tank, or tanky dps, they build that health up, and then they build armor and health items too, and suddenly they have 4k+ health, and if they are lucky enough to have two tanks like that and a back line, you have no hope. Your ad's cant do anything because its 4k health and 200-300+ armor, and your mages are now useless because its 4k+ health... and screw liandry's its a terrible item on way too many mages.
Edit: ARAM is supposed to be fun back and forth all out fighting, but this kinda thing turns it quickly into a "have fun, you are going to be slowly pushed back to your nexus while we pick off a few of you and a tower... over and over again." There really isnt any big fights that happen anymore in situations like this and it really takes any fun out of the match.