Have you thought about starting somethinng new?A new alliance
It's not Sir. To be honest, in the 3 level 10 NPC conquests I've done so far, I've never worried about staging waves. If the NPC is close to you, I would suggest having each attack be big enough to handle 40K warriors (not that hard to do) and just keep them coming at a good pace. It really is only the first attack that is painful; after that, just keep sending 20K+ archers plus some infantry in as many batches as possible and you'll be fine.
good day sir.. regarding your post about conquering a lvl 10 barb.. suppose its right next to your city, how much time interval do you give the attacks from the next waves?