I read Chris Hecker's rle tutorial from Game Developer and I was wondering if that method would be fast in 16 bit and faster than DX fast blit. The rle is used for blitting isometric terrain tiles (a lot of 'em. bout 72 per frame).

I think it would be best to store your tiles in video memory surfaces and use a DX blit. This would be fastest. Accessing video memory from a software routine is slow.