Arvak-

I've watched people pick up 4-piece Tier 6 in the matter of a week after hitting 70. In fact, one of our paladins upgraded from Essence Focuser to Crystal Spire on the last Illidan and another went from welfare to 7/8 in a single reset. For myself--having little or no external support besides running Kara with various alts--it took about 4 months go from dinging 70 to clearing BT, and another month or so before I could consider myself fit for Sunwell progression.

With that in mind, the re-roll curve has a lot of wiggle room depending on what connections you have and how motivated you are to learn a playstyle to extents that reach beyond the whimsical realm of alts. Luck definitely plays a factor, it probably would've taken one month less to get where I am if it weren't for poor decisions. Loot luck also plays a heavy role since it means the difference between spending days or months in reaching sufficient raid-viability.

All I can say is that at this point, the only way I could see someone re-rolling into a top 500 guild before Wrath hits is through some serious connections and possibly sexual favors.