Well for sure its one of the most common combo, but not as common as skinning/lw. Just roll whstever you want since there will be many of each profession.

would be curious to hear more people's opinions on this

Eng is must for pvp m8

Engi is a requirement for high end pvp. Every good guild needs a few alchemists too. Skinning is extremely common for leveling for the extra vendor gold. I would say skinning/lw is common, so is enchanting, so are mining/herbing.

I think vanilla had very even distribution of professions. I can't say what percentages were or will be though.

Since engi is required to be the tops in pvp i would suspect mostly every pvper will run this combo if not it will be engi/x for sure tho however they can make cash for the engi

Almost everyone who pvps more than casually will be an engineer. It was very common in Vanilla.

The projected prevalence of engineering makes me wonder whether it will be a good choice to start with. We still don't know what Blizzard is going to do as far as population caps.

I've played on some "projects" before where mining in the first month or two was essentially nonviable and you were just wasting your time.

Engi is obviously huge for pvp (not arguing that point). But it's also a gold sink. Gold is quite relevant, especially at the beginning.

mage

https://www.youtube.com/watch?v=Mh_cLN66zHA

Rogue

https://archive.org/details/Dahis_-_Dahis-Transformation.__GM_Rogue_PvP_Rogue_2007-01-07_4.50

1) Which class required longer cooldowns in order to be effective? ( Rogues ) (no cooldowns means youre utter shit but they aren't really long to reset)
2) Which class had a better time in battlegrounds? ( Mages ) (Sheep spam, mobility control, ranged damage)
3) Which class had a better time in open world? ( Mages ) (same than for BGS, rogues cant attack group vs group or they get facerolled from the range requirements)
4) Which class had a better time in dungeons / raids? ( Rogues ) (Didn't drink water for ages so never any downtime, WAY funnier than drinking after each fight and summoning water all the time for everyone)
5) Which class was better at soloing? ( Mages ) (Sheep, Mobility control, ranged damage)
6) Which class had more 'outplay' ability? ( Mages )
7) In a situation where a rogue or mage had to do 1v1's with other classes, back to back, which class would fare better? I guess this goes along #1. Half and Half