51 Riftstalker

[Uxor]

I don't see the point in going 51 points into Riftstalker. I go 46 points in and skip out the extra attack power.
The 51 point ability has a way to long cooldown to be viable, and the extra 15% attack power is meh. Instead I go 8 in BD for self heal, constant AoE and Side Steps, which leaves me 12 points for a better bard endurance buff, 20% (I think) more health and a motif which reduces the damage I take by 5%.

This is only for dungeons btw, however in raids I still run 46 RS/8 Rng/ 12 Bard , for the mini heals off Cadence when I've got my threat sorted.

thoughts?

[Muspel]

You do it for the extra endurance from Improved Guardian Phase and the absorption from Improved Rift Guard. Also, Scatter the Shadows is amazingly powerful in certain situations, and can allow you to ignore specific mechanics on some bosses, both in 5-mans and in raids. Even if you're not dealing with high instantaneous burst, it's still a great panic button if you're about to die, much like Defer Death, and having more cooldowns is important on a lot of challenging boss fights.

The healing from Meditative Trance is inconsequential in the grand scheme of things, if you look at the numbers (and how much of it ends up being wasted on overhealing).

Keep in mind that when you raid, you're far more likely to die to burst damage than you are to attrition, and Bladedancer does nothing to help you increase your effective health. You can use BD in 5-mans if you'd like (51 RS/7BD/8RNG is great for experts and decent for raids), but dungeons are so easy to begin with that it's not really worth having a separate spec just for them. If you're interested in learning more, check out the theorycraft section of my tanking guide (there's a link in my signature).

[Adastra]

You also forget that for going 46 RS instead of 51 means that your shield does 2.5% less absorption per hit, although for dungeons, you can get away with running many hybrid tank/dps specs. As far as raids go, the motif "benefit" is gone since you will have a bard in group for that anyway.

I'll agree that side steps is nice, but the BD self heal isn't worth giving up a point in ranger for the 2% reduction in damage. Of course, this depends on what type of boss you'll be tanking in the raid. You won't be running BD if the boss has enough magic damage to worry about though.

[Uxor]

I use the bard motif in 5 mans, and I though that I mentioned that I didn't use BD in raids? But, I agree that the 5% more endurance from improved guardian phase and rift barrier would help, tyvm both

[Muspel]

Spending GCDs and/or combo points on self-healing is generally a waste in 5-mans, unless your healer is really struggling. It's more worthwhile to just use damaging abilities to finish the dungeon faster, since healers spend a lot of time twiddling their thumbs as it is.