I think it might be OP, although I have yet to encounter an AM at all in the few games I have played.That AM aghs is 100% broken. As a support player the constant reflection of spells is fucking ludicrous. It is too good of an item for how quickly an AM player can farm up 4200 gold.
The issue IMO is the backpack, which is what makes Aghs viable. Let's say hypothetically Aghs existed for him in 6.89. His slots would end up being Treads, BF, Manta, Aghs, Vlad's or BKB, and a TP. You don't get the space to go S&Y, Basher/Abyssal, or something else.
Now you can put the TP in the backpack for fights and any extra items you can bring out before a fight, or keep the TP handy when in rat mode.
I feel like the backpack is very much a thing that rat heroes will appreciate.