I joke about this with my guildies, that I'm the holy pally concerned with how well I'll be able to tank in WotLK. Supposedly it'll be easier, because the additional 30% threat from holy damage that is currently given by Improved Righteous Fury will now be hard baked into the regular Righteous Fury, but the Prot tree has been buffed so much in comparision to Holy I'm afraid that it might lure me away. And if the Prot tree is that good, will a tank need all of those talents just to do a 5-man?
One of the reasons I like being a hybrid is that I can do offspec things to allow flexibility in what I do for 5-mans. Seriously, it's so much easier getting a group off the ground if someone can do multiple roles… and knows how to do them.
For example (and a bit of a digression), I was trying to do a normal Magister's Terrace run because I wanted a particular healing drop and I joined a pug. We had three DPS and me, and we were trying to find a tank. I had already tanked the majority of the BC 5-mans as 41/19 (because I hate respeccing and couldn’t figure out where to put the last point) and while I figured MgT would be more difficult I knew I had the gear for it. My group, faced with the possibility they would otherwise not go at all, agreed to let me holy tank it and we'd look for a healer. We got another holy paladin.
As a courtesy, if I holy tank with a pug healer I always let them know I'm off-spec; not so much because I think I'm going to get pancaked and they need fair warning, so much as I don't want them to think I'm hiding something. I always follow this disclosure with a mention of which 70 instances I have successfully tanked with this very spec so they know the level of my capability. This paladin didn't freak out about me being holy, but he asked if he could tank instead. He'd even respec prot. Ordinarily this would sound like a good thing, except that he also told me he'd never tanked before and wanted to try it out.
I had all kinds of concerns, because Magister's Terrace is not exactly a training wheels instance for a first time tank, it's borderline heroic, but we gave him a shot. We died on the second pull. He had respeced, but his gear was unfortunately crap, being a hodgepodge of things he'd found and none of it enchanted/gemmed. He died so fast I barely had time to get off a heal, and it wasn't enough to keep him up. (Tip for newbie pally tanks: Just because you can AoE tank doesn't mean you'll survive it.)
He switched back to holy to heal, I put on my avoidance set (this being MgT I was expecting to get hit enough that I'd need the extra dodge/parry/etc), and even though I was still holy spec, I successfully tanked Magister's Terrace.
Having done so was certainly a feather in my cap, but what concerns me is...
Will I be able to do this in WotLK? Will I be able to tank the hardest normal 5-man as holy? It sounds contradictory considering that I'm not specced for it, but I don't want to tank in situations where I think it'll endanger the party. My tanking gear is all gemmed and enchanted to the same degree I maintain my healing gear. When I tank I use wizard oil and stam food, even though I'm just doing 5-mans. I even maintain two tanking sets, one for avoidance and one for threat, to use based on what the situation calls for. It's just my spec is only 19 points into Prot. My goal was never to be a raid tank, but a suitable replacement in a 5-man.
The change to Blessing of Sanctuary concerns me because I won't have it as a holy tank (and if a prot tank is in the party to provide it, I won't be the one tanking). If that's now a tanking staple, is there the possibility I'll no longer get enough mana back from Spiritual Attunement? Prot pallies might not have to worry about their mana pools anymore, but I will. The change in Seal of Righteousness to draw on attack power in addition to spell power concerns me as well, because I don't what my threat's going to look like. Most, if not all, my tanking gear is going to change.
Of course there's a good possibility Gillien will not tank prior to Northrend now that he has most everything he needs out of Outland, but I'll be terribly disappointed if he gets to Utgarde Keep and can't tank a thing.