Anything is easy if stunlocked I've not been very successful stunlocking dragons though. The only time I managed to took out the one near Geldern in melee I did so by hitting him through a ruin wall that blocked his breath attack.

I found the two cave dragons easier, the cave has a lot of cover options making it a piece of cake for a patient archer…

Speaking of stunlock I've never managed to defeat ogres in melee (they dont stun easily), but they are pretty darn trivial to a mage…