Hmm. 17 over 14 protection, not enough to really mean anything in the face of crossbows, certainly not magically boosted ones, though nice in extended melee combat.
On the other hand, the lance attack is a significant advantage,
when using massed wind lords, as it is an almost guaranteed kill in the first combat round for each wind lord against most opposition. Good for clearing some space.
If I were a 1-1 comparison with the Valkyrie, I would probably still come down on the "too expensive for the benefits" side. However, since I ought to be comparing entire themes rather than individual units, I will not do so.
With their relatively high cost, they look to me to be more to fit a role as support units used in conjunction with, e.g., massed Icarii, for a rapid reaction force with extra punch, or as a heavy flyer component with hold-hold-hold-attack rear in an infantry/chariot heavy army.