Honestly, the real reason why it's not healthy for Aram is because it isn't exactly what it should be.
It's supposed to be something to help champions who are melee close the gap and preform better initiations with team members, where melee champions are usually bystanders in a war of poking and zoning. Which is good, because this is something that can bring balance to the ARAM force - if you will - by making melee champs much more viable than they were before.
The only problem is that, while this item was made to help melee initiations and team follow ups, the utility exceeds that purpose and breaks certain fundamental laws of the game.
Vision is a big problem. You pop one of these snowballs of love into a bush and you can get free sight on an enemy within! A volley of snowballs into the brush can reveal many enemies hiding in wait, where you used to need to use powers and items to grant vision, this item gives it for free. And some champions rely on stealth for their play-style... champs like Twitch 
, Shaco 
, Teemo 
, etc. but now you can completely undermine their play-style by constantly shooting snowballs at them. Shaco, for example, isn't safe charging into the enemy team anymore. Shacos used to dive in undetected to pick off a low health foe, or use his ult from invisibility for maximum chaos... but now he will get caught in the constant volley of snowballs and smashed to pulp before he can do anything. 
Damage is nice on items, but Snowballs deal true damage, a good amount of it. Even with it nerfed - it's still present. It's there to make executing low health baddies easier - but it's unnecessary and broken. Before the patchpeople were shooting these bad boys at everything that moved, even tanks would eventually be widdled down to low health with the constant fire. Even now, champs can use it to hurass low health enemies and keep them from regenerating health... and I've seen it used as a minion executor that's much more reliable than auto-attacks for last-hitting at later levels. Why is a device used to initiate being used by the APC to execute minions? That's not right!
Range is another problem. We all know that it's to get into the fray, but the line of the snowball is a freaking sniper shot! If can outshoot this guys 
Wildcards, This girl's Boomerang blade 
... 
... and that psychopath's Zap! It can very well reach from one turret zone to the other turret zone outright. And while this was probably intended to let initiations be more clever by catching people out who are further back... it turned into chaos pretty quickly. There's nothing worse then being a low health Brand 
and staying far in the back of the battle to snag an inner-turret health rune, only to be snowballed from center-map by an enemy Janna 
.. And even though she's super weak, she dashes to you and hits you with her Zephyr. You die instantly.
Sure, she may get what's coming to her, but things like that shouldn't happen. Players who understand proper zoning should be able to outsmart those little snowflakes in a bundle... but at the range that they currently are at, there is no way to be smart with zoning. A random snoball can spell your demise if your even in the general vicinity of the enemy, and that's not cool.
The most glaring issue of all, though, is the Cooldown. You see, all of these things like damage, vision, range, they may be problems - but they aren't the big one. The big one his how frequently you can recreate the snowball fight from Elf with this summoner spell. Not even 30 seconds between snowball piffs, something that would make the writer of Calvin and Hobbs green with envy - but would make League players red with rage. Heck, they could probably BUFF the other aspects of the snowball if they nurf this one! If they made the snowball deal more damage and go further and grant vision for longer but gave it a 216 second cooldown, people would probably rage less. But as it stands, there is far far far far FAR too much utility in this little ball of arctic goodness for it to be on such a high frequency. Teemo 
getting hit by a snowball then may get ticked that his hiding spot was found out - but they used a 216 second cooldown on him, so he understands how it goes... but where it is now, they can get vision back on the little guy by the time it's worn off and he's gone incognito again!
All in all, there's no reason outright that you shouldn't enjoy the poro ball while its here 
... but just so you know why other people find it so unbalanced!
I hope this helps! 
