> Doesn't this just shift having to protect the gathering unit to having to protect the resource itself?
I'm not really sure what this means; you still need to protect the unit, but you can put it anywhere you want. Mana exists in your inventory and doesn't need to be protected. Golems will fight back while under attack and therefore don't generate mana during that time, but they become productive again immediately when the attack is over.
This strikes me as fairly different from, say, Starcraft, where workers can only function within particular small areas and having them outside those areas deals severe economic damage in the form of opportunity costs. The fact that everything you ever build is made of golems mirrors the Zerg mechanics, though.
But I am not a big RTS person and I find the overall conceit of the genre pretty annoying. There's no such thing as a battle where technology levels change mid-battle. In an actual battle, if you have infantry and you want artillery, what you want doesn't matter because you have infantry and that's not going to change. In an actual military campaign, if you have infantry and you want artillery, you do that by getting artillery shipped to you. You can't make your own.
Civilization focuses on technological development and includes military engagements that can't stand up to even the friendliest critical analysis. RTSes go the other way; they focus on battles and include a rump technology mechanic that can't stand up to analysis. The problem here is that technological development is measured in decades, or longer, and battles are measured in hours. You can't have a working game that does both things.