I don't know what bonuses the GL have on the boss nodes, but with all the data disks equipped plus maybe consumables, I think it should be totally doable to defeat GLs without GLs in the game mode! The bonus on the data disks are just crazy awesome. So don't judge too fast, try and see how far you can go :)
(they did say it's not meant for everyone to finish it though)
Personally I'm having a TON of fun with this new game mode!! I love it!!! <3
My guild members with smaller rosters (~2M GP) are a bit frustrated by the difficulty though, so maybe adding an easier tier would be nice? Though I'm sure they'll progress more than they currently think in two weeks' time, especially with all the special bonus they can get.