I might have to give this game a go, few questions first:
How hard is it?
Does it require a decent computer?
How many people, in general, not just on B12, play?
The difficulty can be set in the mission menu. It varies from Normal (easy) Advanced (the actual normal) to Elite (hard).
They differ in their hardness (duh) and drops from enemies (the reward for the actual quest seems to remain the same).
Oh and if you die you cna restart but at Advanced and Elite you accumulate woounds that cause lasting debuffs that can only be removed by using a specific item (a normal item from normal vendors and drops. not some premium BS) or visiting a doctor at one of the bases.
Later (especially elite) ground mission mobs can get kinda nasty so as an engineer (in theory a tank... at least when in a spaceship) i usually just set up a bunker with turrets, mortars, mines and shield generator and cede the fighting to my AI companions (you usually go on missions with a team of 4).
This way i can actually do Elite ground missions without dying horribly in split second... as a tanking class.
Not sure really works silky smooth on high setting on my PC (AMD FX 6300 six core with 8 gigs or RAM and GeForce GTX 650) and if Angry Joe is to believed you can crank down the graphics settings way down to play on older PCs (not sure how much older tho)
Dunno i came back to it after a several month long hiatus and the Bay 12 fleet roster is empty... i'm apparently the only person in the B12 fleet.
And as for the classes... i still have no idea if engineers are actually tanks in both space battles and ground combat. So far i had more succes in ground combat by supporting others rather than trying to tanks (oddsince you have aggro building abilities among your ground and space skills)
Currently i assume its
Tactical - Space DPS Ground DPC/Tank
Engineer - Space tank Ground support.
Science - Space/Ground support