Now that this has resurfaced (err, I mean bumped), I would pesonally like to say that my first and vavorite Megaman game is Zero 4. Just look at my username? That "4" didn't come from nowhere, did it?
I mean, the sword play is fast, and, after a while, every enemy can be killed with blade alone; buster really is more of a trump card. If they have the high ground, just equip that lightning EX and dash atack the wall next to you; the sword goes in the wall and produces sparks that travel along th floor and damage the enemy. Though thiis strategy isn't needed on normal grunts, it helps on other enemies as well. Try sheilded enemies. Their sheilds don't touch the ground, so electric sparks travel underneath, and one hit KO. Also, the double jump (Yes, double jump. Go visit GameFAQs.) helps in aerial attacks; the double jump extends the length of the dash-jump, thus giving us flight for the overhead. Also, the ice shokwave works well on open stretches and slopes, and passes through multiple enemies. Try it. Yes, I'm addicted.