The meta will add almost 500 armor so a non-meta helm is almost always going to be inferior.
The fact that The Great Wyrm has a lot of Block rating makes it less useful for Progression encounters. Thane's is definitely better than Wyrm
Is it better that the tempered Titansteel helm (come the patch?) you lose 44 parry and 39 block but pick up about 50 stam and 12 defense