Having the option for a +holy damage enchant or having a tanking weapon with straight +holy damage instead of damage/healing would really be nice.
After all, weapons can be swapped out while in combat, so no loss in utility for us at all.
I'm not sure it would really end up being in our best interest, with the problems we face fighting to even be able to tank much less main tank, for our gear to look more "healing" oriented. Sure it would provide more utility when we are acting as offtank. However, we would definitely be forced even more firmly into the "offtank only" role, since we could heal better after our add was dead or whatnot. That being said, the "healing aggro" method on a few fights like morogrim would be easier (but just emphasizes the "offtank only" conundrum).
Right now, I think many of us work hard at trying to be useful to our raid groups and that usually means offtanking and doing whatever utility thing we can to help the raid. Whatever it takes, we do it. Should we have to do that? I don't think we should. I suspect many if not most people who post here would really like for the paladin class to be put on equal footing for maintanking and suspect also many if not most (myself included) are bitter that the deck is stacked against us. The fact that fixes are not only possible, but feasible without being gamebreaking remains painful as long as those fixes don't occur. It's not like suddenly prot pallies would put warriors out of a job, since we are the minority spec of paladin and (iirc) still the minority spec for all tanks.
All that being said, changing the tier tanking sets to pure +holy damage would be nice for threat and damage output when tanking, but would remove some utility when not tanking. As long as we are forced to be (perhaps) the "premier offtank class, not a main tank class - working as intended", we really can't afford to only have +holy. If they fix the class so that we have a level of MT equality or so that our OT role becomes more dps rather than healing oriented, then +holy only on our gear would be fine.
And by the way, our status as "premier offtank" is about to take a hit when DPS warriors get that threat buff in 2.3
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Mavrix
BE Tankadin
Dalaran
http://www.wowarmory.com/character-sheet.xml?r=Dalaran&n=Mavrix