I can see that with the hp, although I feel like Ronan is stronger because of the movement ability and semi-range ability.
That being said, assassin is probably the worst. The unique damage doubling ability is neat, but not super useful most of the time. Nothing besides the boss has over 5 health (on normal mode) and that isn't too tough to get (in weapon damage).
I've been working on a speedrun which is why I'm nerding out lol, they can't put a timer on the top if they don't want me to beat it fast. Weird that the timer isn't shown in the shop or upgrade screen, but is ticking up while in the shop.