Maybe it's just me, but I've found that while in the past I would ride around on my flying mounts both on ground and in the air, with warlords I've kind of abandoned some of my fav flying mounts for just ground mounts.
Mounts like the headless horseman mount and others that look ok as ground mounts I still use, but to me there's something kind of pathetic about a dragon or firehawk mount that has huge wings, but can't fly.