I never played an engineer in vanilla and didn't realize how great it was until BC. It seems things changed a lot at different times. Let's get some informational threads going about 1.12 engineering that we can all use as a resource!
The major question I have:
In this version, can you level as gnomish specialization, make all the trinkets and gadgets, then re-level as goblin specialization while still being able to use your already-made gnomish gadgets? If yes, how?
Post your 1.12 engineering related questions and hopefully some knowledgeable people come along who can provide answers. Links to good 1.12 engineering guides would be great as well. If you have secret engineering related pvp strategies, spills the beans!
Someone already said the key point of the paragraph below earlier but I'll restate it: The difference between the professions in pvp is very minimal at least to me. This is due to the fact at higher gear levels engineering can fall off and
the only really good things out of engineering (reflectors) do not require a discipline to be chosen. The only item you can use from gnomish then switch over to goblin and keep is the Death Ray. That however does not even require engineering to use but it's such a variable factor. Can do 500 damage. Can do 3k. Can do 500 to you, can one shot you.
Some items do not require a specialization to use them, however most of the items that do require gnomish or goblin engineering to make, typically come with the tag "Requires: X Engineering" this was put in place to stop people from doing this exact thing. This is to add more emphasis to your choice in professions and discipline in the line of engineering and leatherworking. Yet, to answer your question the best I can: I can not think of any items where this is do-able and the items tied to a discipline of engineering typically are the for fun items, like World Enlarger. There are no actual items that would give you some immense advantage in pvp. I do not consider the Death Ray because of the fact I've had it kill me before when I was using it. It's more of a for fun item in a pinch. Not to mention using it takes up a trinket slot which once you get to the late game and are rolling with four trinkets (pvp rogue life), it loses its value because you're to replace a static trinket, for a variable one that does anywhere from 500-3-4k damage and has the possibility of backfiring. If it works, great, if it backfires, you've pretty much lost there if you weren't severely beating them into the dirt.
Any engineering pvp strategies would already have been made available. Granted the possibilities with engineering are near endless, you're talking of an era that's been in existence for a little over 10 years now. There are people who know the exact location of every single quest in the game its been that long. Ones I can think of are:
Rogues: Sap + Death Ray, Sap is interchangable with damn near any of our CC effects.
Rocket Boots in WSG because it's a 20 second 50% speed boost.
Mind Control Cap into lava or water.
Warlocks Only: Mind Control Cap then spam Dark Pact on a mana reliant class to drain it all. (Requires 31 points in affliction however and most locks I don't think go that far down.)
Flash Bomb vs feral druids in their forms for the 8 second or so fear.
Cloaking device to "vanish" spellcasts if you don't have access to vanish. (Requires you to have equipped the trinket before the duel/fight however, or out of combat equip then prolong the fight)
Arcane Bomb vs casters. For rogues this is best used 2-3 seconds before kidney is wearing off. It's a massive mana drain, does damage on a percentage of the sapped mana, then is a five second silence. However because it's a bomb it has a longer cast time and can not be done whilst moving. Against a mage I strongly advise a Thorium Grenade.
Parachute Cloak in AB for the slowfall.