This made me lol pretty hard. Why you ask? Because my guild clears Castle Never all the time with 1 cleric and either a GWF or a GF. Sometimes both. I heard if you wanted access to all of the endgame regardless of skill the games on OMGPOP are right up your alley.
The Cat right now is the best pet. It currently grants 100% of its stats to the summoner just like the Stone, but also has an inherent Crit + Recovery buff.