Attack Speed is increased by the Crowd Control stat. Its perfectly easy to use. Probably one of the easiest weapons once you get used to timing your swings, its basically head empty.
Killing > Staggering. But having the weapon have some weakness to counteract its ability to (no ammo limit) deal huge piles of damage to priority targets is a sensible approach. At least, unlike the ogryn power maul, it can 1tap most normal enemies on headshot and can even kill two whole groaners in a swing.
Self stun is fine, it’s basically irrelevant at 0.6s unless you’re just incredibly poor at positioning. The Deimos has such an immobilizing effect. It has a lengthy commit to deal big damage and it’s perfectly usable.
“Meta weapon” is loaded as hell considering we’re comparing a weapon with actual upsides and downsides to things like brainempty mundane axe kills everything with leftclick spam. The fault is Fatshark’s fundamentally failed melee weapon design, not the Thunder Hammer itself. Though I maintain the Crucius needs cleave on powered swings.