I haven't tested one out personally, though I know a few who have. The stat spread is pretty balanced, which is nice, and Waterfall got a nice damage buff in the last update (though its EPS is still quite low) should you choose to go with that over Dragon Tail. As far as charge moves go, I would rock Surf (charges quickly and can draw out shields) and Blizzard (ice provides very relevant coverage).
The only thing, however, that I think holds Milotic back is the fact that it's currently always a second-best option. As a water Mon, Blastoise is pretty much strictly better than it in both the Great and Ultra leagues. Then there's also Lapras, who has access to water gun/surf/blizzard, which should perform similarly to Milotic but with more bulk.
