I'm a little confused as to why you felt the need to grind so early, let alone to level 5! The game wasn't made with grinding in mind at all! :P
You're correct that each guard has different characteristics, but you weren't really able to see it at max level... Not that you ever really do in any game if you overlevel/maxlevel for an area.
By the way, this was meant to be only an hour long for the IGMC, which had a 'soft' one-hour limit.