I started playing this game a few months ago and immediately fell in love with the item. It's unique, it offers you a new way to deal with ganks, and it helps you farm more efficiently without having to use your abilities. The problem with this item is that it's too weak. The very thing that makes this item so awesome is just too ineffective outside some niche circumstances.

You do 50% physical damage as an AoE before armor penalties, with range that can't get anything that isn't directly on top of you. If you could just do 100% AoE and boost that range a little, I think you'd see more people use it. One could conceivably discourage constant ganking through sheer intimidation.

I can imagine someone coming at me with something like "Oh if they buff it then X champ will be invincible." This could be true if the entire enemy team decides to dogpile it. I honestly think it's a good thing though. At least then ganks wouldn't be a simple matter of slowing someone down and then letting sheer numbers do the work.

An item that allows you to 1v2 on it's own is really the definition of broken, so I don't see Tiamat being buffed to that point.

I would like to see the attributes change a bit on it though - there is a significant lack of counter-build AD items for AD characters, some junglers would like AoE for faster clear times, and Tiamat's splash already discourages the RADCs that could abuse it from picking it up - basically, I see it as a prime candidate to be an AD/Armor item, preferably with Armor replacing the Health Regeneration per 5 and Mana Regeneration per 5. It could certainly stand to have a splash-radius increase as well.

Given the fact that bruisers dominate the game at this point in time, something like that would practically be a necessity if things are to be more balanced. As it stands, you can get stunned for a moment, then are left to fight a hopeless fight while two people slow and fling you. With few options for escape, you can either run and die, or fight and hope one of them lags out- then die.