"We added that sigil and enchant because death knights had difficulty reaching the defense "cap" in part because they don't have shields, ranged weapons or often tanking weapons."
1H gives +def
Shield gives +def, SBV, and (+) random stats (SBR, Hit, Exp, Dodge, Parry, etc..)
Gun gives +def, and (+) random stats (Agi, Hit, Dodge, etc..)
"Had this enchant gone live it would have become THE enchant for nearly all tanks. It would not have been an interesting choice. We would have had to keep introducing higher tiers of the same enchant, or else players would just keep using this version for perpetuity. We put Stamina already on many items. We don't think your weapon needs one as well. I received messages from several tanks for very prominent guilds asking us to please not go forward with this enchant. They understood why it was bad for the game."
- TBH I don't know why even complain about it... Blizzards game so they can really do what they want with it. As a DK did I have any issues reaching 540, No. Did I have to plan out my gear to reach it initially, Yes. The question you have to think about in WotLK is: Is Blizzard catering to A) the min/max raider that learns the ins and outs of the class they are playing; or B) the casual who hits 80 wants to run a heroic that afternoon and fully clear Naxx that night?
As a DK do I think the runeforge necessary, No ... Is it necessary so the more casual population can hit 540, probably.
Does blizzard need to make an interesting enchant for prot to use, Yes ... Was titanguard the answer, No.