Definitely a longer exposure; probably in the 2-3 second range for this I think. A polarizing filter would be very beneficial as well. Consider moving around to your left to try and get a more 'head on' perspective, but still keeping the diagonal flow.
If you can get more to the front of it and lower, that would be ideal. You got the right idea, I try to stay to the lower front side that the fall is flowing too.
If you already had a CPL on and your lens was stopped down as far as you could go, an ND filter would be your next option. I get the 3 packs. .6 , .9 , and 1.2. I paid $130 (US) for my set. Dont go cheap, they will only hurt your image going with cheap filters.
I shoot every waterfall I can. I start at F11 and ISO 100 with a CPL. If thats not long enough Ill stop down until I get the exposure Im going for or start adding ND filters. Ive been known to stop down to F22 ISO 100 with a CPL and all 3 ND filters....... The vignetting from the filters gets removed in post.