If the previous Tribes games are any indication, a mouse is required; the slow response of a thumbstick just can't hack the break-neck pace.
Without hit-scan weapons and relatively slow movement speed, depth (as in the third dimension) actually matters a LOT.
In Tribes 2, there was no Wunder-Pistol/Quickscope exploits. There were only two hitscan weapons; one of them sprayed badly, the other took a minimal of two shots to kill with AND drained your entire energy bar; hit or miss.