Riot just dropped a nuclear bomb on laneswaps. Check out the just announced changes!
Tiamat is an item that sounds cool, but doesn't work in practical application. While a five-Tiamat build for Shyvana has the potential to one-shot entire teams, it's not likely such a Shyvana would even reach that point in a game. Tiamat is actually very cost-efficient for the stats it provides. However, those stats aren't really something a lot of champions desire. While the attack damage is useful, the mana and health regen aren't something most champions want to purchase. Tiamat does give the same amount of damage as a B.F. Sword, meaning all of the additional effects only cost 420 gold. However, it can't be upgraded into a Bloodthirster or Infinity Edge like a B.F. Sword can, resulting in a lackluster late game. Tiamat is a simple item to fix. Currently, its effective radius is only 92.5 units in length. Most melee champions have an attack range of 125. Tiamat in its current form just doesn't splash to enough targets. If Riot increased its range to match the melee range of most champions, it would be a perfectly decent item to purchase on a champion like Fiora.