At BIS EP values:
Windsong any hand (61.2% uptime of some stat) = 1144 EP
5.0 Dancing Steel OH (24.2% uptime of agi) = 1094 EP
5.1 Dancing Steel any hand (50.2% uptime of agi) = 2270 EP
These are relatively straightforward to ballpark, the 5.0 MH Dancing Steel value is a bit tougher since it varies with special ability frequency. Just drawing straight from my own logs, on a fight like Garajal I've seen around 70% uptime on dancing steel when I only have it on my MH (playing as combat). With an uptime like that, you'd be talking about 3165 EP. That said, I don't know if this is statistically relevant so I'm putting it here with a big caveat. Overall it seems like their goal may be to keep 2x dancing steel in the same general realm of dps but shift the contribution of each enchant to be a little less weighted towards the MH.