you look on that from the wrong side
there r only two options, a tank pet who tank,and everything else who is worse,and less good as tank
for landfights,there is only the golem as tankpet useful,for airfights the pig,nothing else does have so much hp,and meleeresist,there is only one,other pet whats halfway good as tank,and thats the ogretype,(special patch 21 pet thing,what they now call goliath)
http://pw-forum.onlinewelten.com/yaf_postst4006_question-about-petskills.aspxread there,if you want some info,i postet aswell a link to the whole pets,with all states
and its easy to overview,what pets make sense and what not.
the prob is,if you wanne use "uncommon" or "unused" pets..you r going to use "useless" and "worthless" pets
means.. you r going to lose alot of a tank ability.
pets dont have differend mainresists,or less good,they have all physical def, and 5elemental def.
some r better vs magic,some are better vs meleemobs, but if you get higher from lvl,8x+,you could easy figure out the difference,means.. you wont need any high magic resist on the most parts,if you r going to fight solo,or in small groups, because you tank much better the magic stuff then your pet ever does,and the meleestuff,is part of the golem.
i think you realy should read the link there,and look into all possible pets,its easy to understand,
all what you not find there,is the orgething,and the new turtle.
but keep in mind,this is all for PVM,pvp is a differend thing
the link to the petoversight,is bit downscrolling, and called (clickable wiki) or so.
clickable wiki,from the jp wiki