Higher stamina drain is just a band-aid. It would nicer if there were a secondary stamina bar. This bar would be visible in combat stance only and used for blocking and weapon swings. It would drain and replenish at a much faster rate than the normal stamina bar. If drained completely by spamming weapon swings or holding block too long, it would disable both for a period of time until it replenished to say 15% or 20%.
Savage2 has a great melee system like this. It's worth a look. Free to download and play.
(Edit: If Xsyon had a combat system that took some elements from Mount and Blade, Darkfall, and Savage2 it would be the most epic combat system to date for an MMO).