If you sub any skills from any other class they are a little weaker and cooldown is longer. But so far it works.
Example. Main, Gladiator and use a Pug skill Second Wind ( used 250 TP to restore HP) the recast time is 1:30 sec. and heals for about half. If you use it when Pug is main recast is 1:00 and heals at normal.
If you are Conjorer Stoneskin is an AoE for anyone around you. If you use it as a sub skill it is not an AoE.