Therefore, the engineering helm is potentially the most helpful item in getting the drop for a replacement. Then, if you get that final drop, the instance is cleared anyway. It's all farm content at that point, so the equivalent item isn't necessary.
Thus, the engineering helm, assuming it's upgraded, is quite nice and at each new tier retains its use. However, JC will diminish unless new JC-Only gems are made since, eventually, epic gems will be introduced. Furthermore, the JC trinkets are not always best and can be replaced much easier.
Blacksmithing, however, will always be incredibly strong and probably strongest. There are a few crafted BoP items that help immensely as well as the two extra slots (which are, at worst, equivalent to enchanting).
Finally, let's not forget the engineering helm is 60 base defense, 21 meta defense, and 16 yellow gem defense. This makes it 97 defense in a single slot. The blacksmith helm, by comparison, is 46 defense. The best instance drop gets is 83 defense, but has 52 stamina compared to the engineer's 112. So even if you were a blacksmith, the two sockets would net you either 48 stamina or 32 defense.
Arcane-Shielded Helm will grant 73 possible defense with only 93 stamina. So the engineering helm is still ahead by 24 defense and 19 stamina - the equivalent of 2.5 gems.
So the engineering helm is strictly better before the four horseman helm, at which point you begin to have similar stats. 4H is widely considered the third to last boss, and sapphiron / kel'thuzad aren't exactly complicated. Again, you're pretty much done with the instance.
Simply put? Engineering is a pretty good choice just for the helm, and under the assumption new helms will be introduced. The trinket is handy, also, as no other trinket offers a stamina + threat increase.
An ignored benefit to engineering is goblin depth charges. They deal ~2500 fire damage in an area blast. Consecrate is 8 (or 10) seconds and cannot move. A misplaced consecrate can easily lead to a few dead or a wipe. This essentially gives you a back up consecrate, albeit at ~2500(1.43)=3575 INSTANT threat instead of ~250(
Finally, there's the handy pvp uses if you intend to do anything besides tank. Rocket boot enchants are probably the best thing in the world for retribution currently. Also the 3000 damage ranged trinket with the 1500 damage glove enchant are very handy.




