I havent , but my 5+ years of SMN expierence says your Wheel Spirits will gain access to Tier 5 spells at the same Level as a BLM . Its possible it may be available sooner , but probly not . Capped Skill isnt required for the SPirit to cast said spell , it just makes it more likely to do so . its generally accepted that Skill 1.)reduces time between Casts of spells 2.) AI used to choose said spells (Tier vs. AM , Enfeebs vs Nooks , Damage vs Enhancing i.e Spikes and En- ) 3.) who or what will be targetted (@ 300 skill i have seen Light Spirit hit my PT with Curaga 4 , but with 315+ i have seen it cast on Out Side PT with-in the Alliance ??!! Same goes for Dark Spirit . @300 it will use drain , but @ 315+ i have seen it use Sleepga 2).
A small added note on this : Your skill is determined by what it was when you summoned said spirit and Swapping gear with a Spirit out , no matter if it raises or lowers your skill numericly will cause you spirits AI to be reset to lowest numbers , sometimes making it not cast at all . so basicly dont swap gear if you are using Spirits .