Professions offer gear, sure, but it's useless gear that's worse than what you get in raids. Charms are boring to grind, but basically mandatory if you raid, but since you have to get them anyway it doesn't matter. Faster leveling doesn't give faster gear, that doesn't even make sense.
So, we're back to where we started, which was that buying level 90s doesn't have any negatives, and until you can buy actual gear, highest ilvl PvP/PvE gear, what they sell on the shop doesn't matter. Simple as that.