Maybe in large parties where others can cover your defenses.. but I dont think kin is a good solo primary in general. Recharge doesnt work on pets, and with the limited dmg cap on pets, even fulcrum is kinda meh. The -res most other sets have probably does a good job at getting the same effect. Even the res kin effect doesnt include lethal. In large groups that cover your weak defenses kin is great cause.. well having a kin in the party is generally better than not having a kin in the party. I have a 50 nin/kin and have tried all sorts of crowd control and provoking combinations. pets just drop like flies solo if you up the difficulty even a bit and even a minion ends up not being crowd controlled.
With the res special IOs that give +35% res to all, a res secondary and inherent res some primary sets can hit res cap which makes pets a lot easier to heal.
Beasts have S/L (but the wolves have less at 16% rather than 26, still cap-able though). Mercs have S/L. Demons have S/L. Nins have none (lol), Necro has smash but not lethal plus a ton of others. Bots has lethal but not smash. Thugs have none except the bruiser that has s/l.
S/L res primaries pair well with res sets, nature is solid with beasts so far. I need more cdr, but when you have the absorb plus HOT going they are practically unkillable.
I also think all MMs should be provoking bosses/elitebosses/AVs to prevent oneshots on pets. Though with max resists they might still not get oneshot.
I have a 40 beast/nature so far and its working fine. Most of your aoe comes from the dire wolf. And things ramp up once you have all pets so they can better stack pack mentality. Each stack is 2% dmg and 2% crit chance which adds up. If you pickup some of MM attacks you can keep pack mentality higher. The hawk in particular can be used for force feedback. And if you want to do damage it can fit a lot of dmg procs which bypass AT damage penalties. With only one stack of wild growth (cause i still need recharge). Primary attacks also have -fly.
Beasts also have about 10% inate defense, plus the special ios and a modest -10% hit from something (like spore cloud) they are aoe def capped.