Why physical (DPS) jobs cross-classes lancer? & Implications

Well even though SE loves to lore us, even when it shouldn't be used (LOOKING AT YOU GC-FRONTLINES), it couldn't get around one blaring issue, TP. Though it would make more sense for jobs to, at times, use another job for X-Class support skills; the current armory system hinders this. Each class is forced to learn the same amount of abilities at the same levels, white mage recently got SSII which changes it a bit, which limits the "creativity" of each job's abilities but at the same time allows them to "save resources" by not having to remake essentially the same skill for each job.
What this means is, cross class skills aren't necessarily there to give us choice/variety. They are there so SE doesn't have to recreate a the same job skill in a different flavor for each job. Thus, each DPS that needed to regain TP was given lancer sub for invigorate and monk for recovery options, second wind. Mages have a similar issue when you look at them all having swift cast but that is impart due to the lack of caster jobs.

I didn't find the right solution from the Internet.

References:
http://forum.square-enix.com/ffxiv/threa...er-Implications

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