Miners are given Toughness, an ability that at max rank, awards +50 stamina. This is a lovely bonus for tanks! A tank's talents will take this well beyond +500 hp, and stamina is also multiplied by buffs and talents such as Blessing of Kings (and not all stats are). This is also going to be helpful in PvP, where stamina is especially important.
Herbalists get Lifeblood, a self-heal, that at max rank, awards +2000 HP over 5 seconds on a 3 minute cooldown. This can be used in or out of combat, and the spell effect entails flowers sprouting up from the ground all around the character.
It is difficult to gauge the actual benefit of this ability across classes and in different situations. In the last few seconds of a close fight, where it is you or them, even a small boost in HP could bump you up to victory. Then again, tanks benefit more from stamina due to talents that factor in your total stamina to then award you with extra stamina (Sacred Duty), increased power (Touched by the Light), and other benefits. It is also difficult to say whether an extra boost in damage might also be worth more than this small heal in a tough spot.
Almost all classes find this ability helpful while leveling and soloing. Raiders will often use it to top themselves off or buy some time until their next heal.
Skinners become Masters of Anatomy, and gain 32 critical strike rating, which is equal to 0.70% crit. This is especially useful to classes who have talents that boost stats based on your crit rating, increase your crit by a %, or where your crit rating actually grants you other stats, such as mana for holy paladins.
The Skinning and Mining bonuses equate to about 2 gems worth of stats, and Lifeblood is all about how you use it.
Conclusion and Comparison
As you can see, for most of the professions, the benefits and stat increases are approximately equal. Let's use spell power to demonstrate this:
- JC: +39.
- Enchanting: +38.
- Inscription: +37.
- Tailoring: 250 SP for 15 seconds of every 45 seconds+. This averages to +83 SP in ideal conditions (meaning, it procs on your next heal after the cooldown is up). In fact, it will likely always be under, though somewhat near, this ideal. A more realistic average is +75 SP.
- LW: +37.
- Blacksmithing: +38.
- Engineers: +18 and a parachute.
- Alchemy: +37.
Still, there are several that are still worth taking, even over other options available for that slot. The Tailoring enchant noted above is currently being debated as OP, and may be subject to tweaking in the future. It is also worth noting that because this is a passive proc, it is not always going to be utilized. You might proc it near the end of a fight, for example, or when you're topping someone off between pulls, and waste most of the added spell power.