The mako is instant hit canon.
I've seen gods of sniping on CSS that have slid down a 45 degree angle slope ramped into the air and did three spins in the span of 2 seconds and then still shoot some guy way the hell ont he other side of a gigantic modded map in the head. It wasn't even classified as all that amazing by the people who practice these things. It's well within the realm of possibility an ordinary gamer like myself could easily snipe and one hit kill the hammerhead like nothing.
I know that it's basically a hitscan weapon, but it isn't instant, it does travel at a speed that can be measured. Not that it matters, as in-game it may as well be.
I'm speaking as if it were an actual thing. Lore-wise it would have a delay.
I've often wondered exactly how the Mako would get back up into the Normandy after a mission. Can it fly? Does the Normandy have a tractor beam? At least with the Hammer head we know that, yes, it can, in fact, fly. Not that you ever see it doing so outside of a loading screen.
Speaking of which, is it just me or does ME3 have shorter loading screens than ME1 or ME2?