It has nothing to do with the mana. Biscuits are better than normal health potions, with or without a need for mana. The immediate health has saved me a number of times. The 10% longer duration on elixirs is nice too. Meanwhile, the other two masteries at that tier do exceptionally little for a support Shen. All in all, it's a pretty weak tier for support Shen, but this is still the best mastery within it.

I got mastery 7 like the day after I posted this guide. So that's something.

I've been running a different rune setup - Flat MR Glyphs(more mage supports lately), scaling health seals, Flat armor Quints and Marks.

Courage nerfs make it less appealing, but there's still nothing better. It's still nuts, especially early on. A good level 1 taunt can be phenomenal. Still, I've been getting the tankier runes, dropping Movement Speed Quints in favor of Armor.

Eye of the Equinox is more appealing than it's ever been, but I was taking that before. I've found myself getting the Black Cleaver earlier on lately. The stacks are good, the movement speed is great, and the CDR is important, especially since Redemption has been nerfed.

Zyra is super common lately, at least at my MMR, and that's not a particularly good matchup.

I've also been buying Elixir of Iron at level 9 a lot. 500g for +25 Tenacity, 300 health, and the movement speed for teammates can be tremendous during early teamfights. Level 9 or 10 also tends to coincide with a back in which I often don't have a ton of gold to spend, though I'm not sure why that is.

I'd like to update some things here, and probably will as soon as I have time.