Nitro Boost and Healthstones share cooldown?

[Tya]

I've only really taken Engineering for the Nitro Boost, which is really handy from time to time, as well as the Springs. I'll reserve judgement, but I'll likely swap out Engineering for something else depending how it shapes up.

Engineering has;

4 teleports.
Unique auction house vendors in Dalaran and Shrine.
Personal repair bot that can be used where the vendor mammoth cannot (Jeeves).
Tons of toys. X-ray specs, gravity well generator, shrink ray etc.
Glider.
Personal invis pot (not 100% success rate, but if it fails you can just pop a real invis pot anyway).
Ability to salvage mechs. Not useful in MoP, but it was in the past and may be again in WoD.

Even without nitros, engineering will still be a great prof to have on your main.

[ComputerNerd]

Engineering has;

4 teleports.
Unique auction house vendors in Dalaran and Shrine.
Personal repair bot that can be used where the vendor mammoth cannot (Jeeves).
Tons of toys. X-ray specs, gravity well generator, shrink ray etc.
Glider.
Personal invis pot (not 100% success rate, but if it fails you can just pop a real invis pot anyway).
Ability to salvage mechs. Not useful in MoP, but it was in the past and may be again in WoD.

Even without nitros, engineering will still be a great prof to have on your main.

Not quite sure about the continuation of the invisibility, as I consider that combat modifying.
But overall you do have a good point.
People get so hung up on a few cherry-picked perks of engineering, they choose very deliberately to ignore the rest that don't support the argument.
Engineering is a lot more than it's tinkers.