This is definitely a strategy, not an exploit. In FFXI there were a few fights that could be won faster, better, etc. with several people onthe same jobs. Dark knights with Kraken clubs for the Absolute Virtue fight comes to mind, as do Summoners using Leviathan in the Fenrir fight.

Speaking as someone who has gone into pvp on FFXIV as a healer and found myself the target of any other type of job who spotted me, I find this thread rather amusing.