I can't find it anywhere: For how much Lifeblood (Herbalism) heals you at lvl 90 and how much haste it provides in percentage + how much stamina Toughness (from mining) gives you at 90? Wowwiki shows only lvl 85 ranks.
Lifeblood heals you for 15000* and provides 2880Haste for 20 Seconds and Mining gives you 480 Stamina.
*Value: 13875 to 16125
I had both on my Tank until I chose to let one go for the Profits on another Profession and decided that Herbalism should remain. Haste increases Resource regeneration ant Autoattacks (which also provide Tank abilities boosts for certain tanks) so combined with a Heal every 2 Minutes I believe it's a better Perk than 480 Stamina.
Well Wowwiki which you claim to have read shows that it can crit and I cannot confirm or deny that since my Tank has very low Crit and it would take hours of testing to verify.
Wowwiki also says that it does not scale with Spell power, and when I had posted what the code says before, "Value: 13875 to 16125" which has no AttackPower or SpellPower multiplicators. It does benefit from increased Healing though.