no
you're right should be more like 45
when you pay attention to the lore the spess mahrens are loving ridiculously op, power armor can take tank shells right to the chest and the heat of the blast will cause as much discomfort to the marine as the force of being hit in the chest with a goddamn tank shell, and bolter rounds are literally small rockets with HE warheads
basically all that's dangerous in single combat to a spess mahren is another spess mahren, hence the weapons and armor being basically overpowered isn't all that ludicrous. you could put together a dm of a single marine vs five other players or something
also power armor's stuff to make you faster is to compensate for its own weight, you'll still be a bit slower than a non-power-armored troop
as for balancing the numbers:
Change armor and health values; 150 health (slightly more than a normal human from all that genetic modification) that regenerates slowly, 150 armor that does not regenerate normally (armor pickups?)
Normal marine armor can jump ~half its height (essentially vaulting low walls)
Devastator marine would have 200 armor instead of 150 and move slightly slower, cannot jump
Assault marine is just a normal marine with a jump-pack (ie, they can jump and jet, not much fuel but fairly rapid recharge - maybe 5 seconds leap and recharge in 4 seconds - rather than normal recharge, on release of jet, fuel is set to 0 and 4 seconds later, set to full)
Bolter: 30 damage, moderate fire rate (~3 shots per second), moderate spread (large enough to miss a blockhead at 32 block range, spess mahrens are not and have never been anything other than frontline troops), 30 rounds then reload
Bolt Pistol: 24 damage, moderate fire rate semi-auto, less spread than a regular bolter, 16 rounds then reload
Heavy Bolter: 36 damage, slightly faster fire rate (~5 shots per second), same spread as a normal bolter, incurs speed loss for non-devastators and restricts jump-jet usage while carried, 400 rounds then discarded
Multi-Melta or Heavy Flamer: 4 damage per tick, ticks one raycast per 0.2 second (20dps), ~12 block range, double damage vs armor in case of Multi-Melta, double damage vs health for Flamer, speed loss/no jump-jets as per Heavy Bolter, approximately 30 seconds worth of fuel then discarded
Lascannon: 80 damage, 150% damage (120) vs vehicles, when hitting an armored marine deals up to 50% damage to the armor as if it were a vehicle (up to 60 damage, or less if less armor remains) and remaining % of base damage is dealt to health, 5 shots then discarded
I would totally script these if i scripted anything anymore