I think Treeko actually does quite well with brick break, a move that I don't think has been mentioned. It lets Sceptile sweep the dark E4 and do well against the ice one. With Dragon claw, Sceptile can beat the E4 basically singlehandedly, and the champion too in Emerald. Ice Beam Dusknoir is a pain, but other pokes can deal with it. The massive water regions are good for training, so you can up for lack of training against Flannery.