DoubleD i think you are confused.

The raw number doesnt matter. All that matters is the % relative to other classes. Thats what dps class balance is.

If a Monk did 10,000 dps and a Bard did 9,995 then thats 5 less still but the Bard and Monk would be doing basically the same dps and there would be a HUGE imbalance.
If a Monk did 10,000 dps and a Bard did 9,000 then thats a 1000 dps difference but it would not be imbalanced at all because Bard would be doing 90% of the Monk's dps which is better than it does now!

Mobs have X amount of hitpoints, and you generally want them to die in Y amount of time. The actual numbers DO NOT matter, only the ratios.

You said "say a bard ends up doing 1,000,000 less damage points than a WAR/NIN/DRG 3~4 years down the line." In that scenario, the mob will have BILLIONS of hitpoints and the Bard doing 1 million less overall damage still only equates to several seconds' worth of dps due to stat inflation.

Think of it this way: if Class A does 50% the dps of Class B, it will always take Class A twice as long to kill things. It doesnt matter if their dps is 500/1000 or 44,444/88,888. (unless you are killing the mob in 1 hit, but thats not the kind of content being discussed)