Most importantly, Axew is not canonically a dual-type.
Besides, there's already way too many dual-types when it comes to dragons. A pure dragon line is a blessing - and Axew's line is the only line that keeps that pure Dragon type throughout all stages, if you don't count Druddigon, since it doesn't evolve.
Without Physical/Special split, the second typing was necessary, as Haxorus needed a STAB attack that used his physical Attack stat. But even with the split, I think it doesn't make it worse. Yes, you can't use it against Psychic-types, but Dragon Dance turns it now into a fearsome sweeper, with incredible coverage with its two STAB moves (rounded by Earthquake). I have a lv 83-84 Haxorus in this hack, and I'm telling you, it is amazing.
Also, I don't understand your complaint about Pineco, because Protect is a move that Pineco has at level 1 in the original games, that isn't something of this hack. And about Psybeam, maybe it should be Confusion, but I see it fine...