There are probably about 15 people working for Mantic now. The operation is pretty small. However, last year they had a healthy turnover.
Kickstarter is not just for small companies. Kickstarter is all about community funding for new projects regardless of the company doing it. Mantic probably didn't make a lot of profit on this KS campaign but what they got out of it was cashflow. This allows them to accelerate their plans and really get a feel for what the community wants. This is exactly what kickstarter is for.
Warpath is immature and not ready to take on 40K yet and needs a lot more development to do so but expect a similar campaign for that in time. Also, don't forget there is a whole new game coming later in the year which should be massively popular.