To me it seems like Goliath becomes way stronger than any other ship once you have a lot of upgrades. Basically impossible to kill someone playing it safe with a max upgraded Goliath
Upgrades are designed in such way that Goliath benefits from them more than other aircraft.
Defense: +5% per upgrade. Goliath gains the most, while a Mohawk (helicopter) with 2 Defense upgrades blows up from a single Predator (default) missile. But you still need those 3 or 4 defense upgrades to survive a stray missile, or more importantly - a Prowler.
Speed: extra speed is not much needed on already fast aircraft, sight distance is limited and human reaction is limited.
Energy: it lets Goliath deflect and shoot more often. Others are not as energy intensive.
Goliath is strong, and I haven't seen a very good player playing it (I was leading the list with it for some time). But I think a Mohawk (helicopter) player would eat it whole. Mohawk has high rate of fire so reflecting missiles isn't much use. It's also fast and its missiles are fast, so it should be like shooting a fish in the barrel. Oh, and you can strafe!
Impossible 1-on-1, maybe. Bring friends/enemies and a Goliath goes down quick, especially if you can time your shots as the Goliath is deflecting someone else's.
It doesn't. You can take it down fairly easily with the prowler. Takes about 3 shots. The prowler easily takes out Goliaths and Mohawks. It's a great unit.