In the comments to the previous post, Kadaan makes a very strong case that Arcane Mages have to balance between Damage and Longevity stats, and have very similar tension in gearing as healers and tanks.
So why are Arcane Mages special? Arcane mages possess a spammable, high dps, high mana-cost, unsustainable nuke in Arcane Blast. Because Arcane Blast cannot be spammed for the entire fight, an Arcane mage has to use what Elitist Jerks calls a "2-cycle theorem of spell selection," where they alternate "between a mana intensive burn mode and a mana efficient mode." The burn mode consists of spamming Arcane Blasts and the efficient mode is usually something like Frostbolts or Scorch.
Getting the correct ratio of burn mode time to efficient mode time to maximize damage done is non-trivial, even before you take upgrading gear into account. It's a Linear Programming problem, and can be solved using the simplex algorithm for a given initial gear set and fight length. Under this setup, Longevity stats are valuable because they allow you to increase the amount of time in burn mode, which increases total damage done, even if those stats do not increase the DPS of either mode directly!
In a lot of ways, it's very similar to paladin healing mechanics, in that we have a burn mode, Holy Light, and an efficient mode, Flash of Light. The major difference is that the spell paladins use is dictated more by incoming damage in the short-term future, rather than attempting to maximize total raw healing done.
However, Arcane Mages are very different from most other DPS classes in the game. Most of the DPS classes use the simple DPS algorithm that I've outlined before. They have a single, sustainable nuke (Sinster Strike, Shadow Bolt, Fireball, etc.) that they rely on, while juggling cooldowns for certain higher-dps abilities and lower-dps enablers. I'm not sure I know of any other class that uses a 2-cycle spell rotation. Perhaps Balance druids with Starfire and Wrath.
(Note for the random DPS who seem to think I am putting them down: the simple algorithm is only "simple" in comparison to the 2-cycle algorithm. Please do not interpret this as me insulting you.)
Now, should more DPS classes have a setup such that they have to use a 2-cycle rotation, and thus increase tension when gearing? Maybe. However, one issue is that a burn mode can be quite devastating in PvP, where burst damage is more important than total damage done. Arcane Blast keeps this in check by making the mage take time to ramp up to the high-dps setting.