Well I had the guardian cm and here is what I noticed - your pet does like 0 damage both with and without being a guardian. Consider this the guardian cm allows your familiar to attack if you get hit. Im not sure if it will attack if it gets hit but I dont think so. So this means you will need to get hit at least once with each new familiar you summon. This can be risky. Also and this is the most important thing about the familiar. Notice how often you get a familiar and what level it is. ex. the level 39 Familiar spell you get summons a level 29 familiar. So your familiar is already 10 levels lower when you first get it making it con green in one level. Considering when you get the next familiar at this point at level 49 the one you just replaced is 20 levels lower. How can something that low in level be of any use? Think of when you are a few levels outmatched and you do way less damage then try to compare that to a pet with no buffs that is between 10-20 levels lower.