Could you advise which of the three is better to choose: "Storm Wind," "Granting Protection," or "Granting Blessing," considering that there are only two slots available?

Even against a Necromancer, "Storm Wind" isn't that great – it's not worth taking up a slot, and it's even less useful against other races.
All dragons and wyverns rarely participate in battles, at least not in large numbers, with the possible exception of certain maps with many high-level creatures (e.g., "Dragon Pass").
And, of course, this skill is useful for capturing Mermaids.
Against Elves, Dwarves, and Mages, mass evasion + protection is particularly effective, but blessing with retaliatory strike is also good.
Archers, Latniks, and Griffons are very sensitive to blessing/curse – and these are always the backbone of the Haven army, although sometimes it's beneficial to take a couple of single Inquisitors to bless your own units.
Against Demons, Mages, Dwarves, and Dark Elves, it's beneficial to take "Fire Protection" (from the School of Light).
And against Orcs, it will be very effective to take, in addition to blessing or retaliatory strike, also "Readiness" from the protection skills – then the defensive strategy of archers will be three times more effective, and the often useless 10-15-20% increase in retaliatory strike attack will also play a role (racial ability).