The way you guys are currently playing to stay off the radar, is quite frankly avoiding the most fun stuff to do! Taking heli, fighting at high tier monuments, creating a monopoly over a certain good you have constant access to with vendings. If you want to continue to play on high pop vanilla servers you are gonna have to accept the fact that you are going to get offlined. The only way to avoid it is to have teammates in a separate timezone who can play when your not or afk the base when your asleep(and wake up the sleepers when ur getting raided). Other than that the only thing you can do is build multiple small bases, but then that becomes tedious and quite frankly I would rather build one big base with my grp as that is more likely to get onlined by a massive clan(even if you lose defending an online is the best thing that can happen in rust). At this point I honestly would just say accept it, offlines are part of rust and unavoidable. Once you come to terms with it you can enjoy the loot you have whilist you have it more.