Tsu's little unscripted guide to Vaseraga movement -

Notations, Attack / L (Square/X) , Unique / H (Triangle/Y), Dodge (R2/RT)

1. L -> Dodge -> H -> H -> Dodge (before full swing)
2. H -> Dodge (after the full swing)
3. H -> Dodge ( before full swing)
4. repeat 2 and 3 and with the correct timing you should never see the slow dodge (your dodge timer will never run out if done correctly)

side note: if you get the slow dodge, don't fret, you can press H again and still keep it the movement going.