It is not in any Gamemaster's control whether the NPCs spawn under the map - it happens when the platform tool isn't 100% compliant with the current map's contruction. If one realised this, they would see and understand why it doesn't happen on certain maps. The problem has been around since the tool was released.
With the various Health for NPCs, there can be many reasons behind it. The main one is due to the simple fact, more NPCs = More Server lag - and when that happens the compliaint amount is a lot more. Furthermore, some NPCs will be gifted more health than the average due to distracting and slowing down battlions like Inquisitors + Starfighters - some NPCs may even be intended as 'heavys' and/or 'bosses'. In addition, any event with NPCs having low health will result in a short one, then we get more complaining that 'the event was too short' - not every map is suited for huge scale assualts, so we improvise and create solutions (one being to incease health to slow them down and create an ending feeling of accomplishment/satisfaction). In connection with what you said regarding teamwork, NPCs with higher HP encourages that - it pushes them even more to work together and coordinate efficiently (just as if you were playing a round of Black ops Zombies and the higher the round = increasing health - thus increasing satisfaction if completed successfully).
As any Gamemaster knows, there will always be a compliant with varying topics. Furthermore, any experienced Gamemaster will agree and understand the way as how we run things currently. The little things you complain about is a compilation of solutions from a lot larger, previous, complaints.