Most (if not all) of the pre BC instances as long as you can hold hate you can tank without a single point in Prot. Into the BC stuff, I would not recommend tanking in a different spec. Ret is still very good into the low 40s where, unless you keep your gear completely up to date, Ret DPS starts to level off. This mean theoretically you should be able to hold threat as a Ret just fine, and assuming you're in mail pre 40/plate post 40 you'll be able to take the damage of tanking. Pre BC the biggest reason to take Prot talents if you wish to tank is to hold threat better: Imp RF, Holy Shield, BoSanctuary.
As for specific parts of your post (geared toward pre BC as that is what the OP is asking for):
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Should I get Imp Righteous Fury - I really dont seem to have problems keeping agro in questing groups so far w/o it.
It's not just for building more threat, but for it's damage reduction component as well. If you as easy enough to heal, and hold threat no problem, not a lot of reason to spec for this.
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Also I'm a big fan of Blessing of Might and don't seem to use Judgement except once per fight
My apologies, but I seriously did laugh a tad right there. I can understand not having time to judge more than once right now, which is fine, but later on fights will last longer and judging often will be a lot more important. What I laughed at was the BoM though. I haven't used Might on myself since ... well ... I can't remember the last time :P Fact is the other Blessings are so much better than a tiny addition to your DPS. If you're Ret using SoC that's one thing, but other than that physical DPS is going to be a very small part of your over all DPS, and tanking it's a pitifully small part of your threat.
If you wanna tank, go Prot cause it will make things SOOO much easier. If you think you are ok without it for now, speccing Ret would be the next best choice. Holy levels the slowest and really couldn't hold the threat to be any sort of a tank.