I am wondering about professions for Druid Tanks.
I am currently doing Herbalism and alchemy. A big wast. What about leather working and enchanting?
Would give two extra enchants (Rings and Wrist)
Wowhead suggests engineering. Not sure about that.
What do you think?
It depends 
Jewelcrafting is currently the strongest prof for any class. The tripple gem bonus easily outweighs any other profession, until we get epic gems for the general population, the gap is closed somewhat.
Leatherworking is awesome too, its provides a stronger stamina buff than others and it couldn’t come any cheaper to craft for yourself.
Engineering has a phase 1 BiS headpiece for druid tanks. Combined with insane utility its highly preferred but can’t be expressed in stats.
Any gathering prof is generally weaker than crafting profs.
Have a look here as well:
https://www.wow-professions.com/wotlk/wotlk-classic-profession-bonuses-perks
I couldnt find a better list but I already noticed some items missing. For example, for LW it only lists the wrist enchant while LW can also craft a better leg enchant, 55 stam+22 agil versus 45 stam+15 agil for the regular one. So the bonus for LW totals +72 stam and +7 agil. Only JC beats that with 3x39 stam bonus (117).