At some point it is not worth it to go after Blackguard bases. If you lose one time, the best you can do by winning on a second attempt is to break even (in the gold). Â I'm working on a theory to leave BG bases alone, only try to remove mercenary bases, as BG cant attack you, only other player controlled bases. Â Then I should get raided less. Â maybe?
The max level of NPCs is 60. Carrot Feeder is a walk in the park once you upgrade your troops, barrage, artillery, shock, critters and have decent attacking statues. I usually take it with just 4 level 8 Sco (the other 4 LCs are 2 Heavies and 2 Zookas and I do not deploy them on most of the NPCs) and sometimes even with just 2 Sco (when I am beated up after an attack). If I have only one Sco left, then I will send the rest of the troops. There are much worse bases with maxed out 4 SLs, 3+ BCs, tons of cannons, and 3+ RLs.
However, once you level up your troops all NPCs can be taken down with no losses (or almost no losses) without boost.Â
I am at HQ 20, XP 51, VP 800+, all LCs 20, Sco 8, Heavy 21, Zooka, 20, statues: TH: 33+14, TD: 28+11+11, GBE: 39+16+15, RR: 50, PSC 67. Most of the players, which I encounter, are level 62-63 with two ice MPs and two protos. If they don't boost ice and they don't have two DCs, then I can take them down from the first try in 80-90% (and without boost).
I usually attack NPCs after I got beaten up and have only a handfull of troops left. I think that the extreme was when I had only one Sco left, 2-4 Heavies, and 4-8 Zookas (can't recall precisely). And it still worked.
My personal opinionated hardest bases would go to Recoil and Shock Therapy. Though I've learnt to take both with Tmed, no losses.