Gloom mines make each other explode, so you usually only needed one Hatchling (equivalent of the Dretch) to blow up most mines places in a tight hallway. Camping in Gloom is way different from Tremulous, merely because the base structures are much weaker, and every Alien class can attack the defenses. Apart from that, Gloom had sported some serious explosives, which more often than not resulted in someone at least once per game mis-dropping his C4 or mis-aiming his rocket (or better, have a small Alien 'catch' the rocket), which meant most of the team and their defenses being blown up. That said, do not think Gloom was without camping, it's simple rock-paper-scissor system allowed for easy camping, only it was(is?) much less dependant on the base.
Thanks to a certain coder taking over the main Gloom development and making changes to the game he deemed 'cool', Gloom games would drag on and on and on and on and on, helped by some serious chokepoint maps, where the only thing between the Human and the Alien base would be a hallway about as wide as the hitbox of a fat Alien (Stalker). In this regard, Tremulous games are far less stale, and much more susceptible to change. This is all what I think about it though, I haven't been with Gloom from the start, so I would not really know how it was in the early days.
A side note: If you make mines cost build points (which is logical) the chances of them being spammed all over the map and actually being useful are rather slim.
