If you mainly solo you want to max any and all pet defensives ASAP. Mainly: Companion's Agility, Elemental Agility/Durability, Sturdy companion as you mentioned, Companion's Durability, Fortify Companion. And anything else that would raise pet hp, increase its avoidance, decrease maximum damage they take.
I would definitely recommend getting hastened Fort line at some point b/c it does cut the time down I think from 30min to 20 or 22min (Could be more, i don't remember off the top of my head). Also, I would STRONGLY recommend getting Mend companion and Replenish companion lines maxed, b/c even though we have mercs they still tend to smurf-up and this is our oh smurf button for when that happens. Also, getting your Gift of Mana lines done will help greatly with your mana pool, so that on the off-chance it procs you can cast a Rumbling Servant for only 1 mana instead of around 3k mana.
As for pet offensives I would get: Companion's Alacrity/Fury, Elemental Alacrity/fury, FBO and extended FBO. Pretty much anything that will increase their amount they hit, the damage they do, and how often they hit is quite beneficial to any mage.
For yourself it depends really. For example, we got the spell Jolt of Many which allows us to nuke with 1 spell 7 times for a set amount of damage. However, you need iirc 9 pets on the mob to get the max effect of the spell so you should probably invest in Host of The Elements line of AA. They are not a huge increase in dmg themselves, but with using Jolt of Many (along with getting a lot of spell dmg) they become quite powerful to a mage. With that said, I would probably get your Destructive Fury, Fury of Magic, Spell Casting Fury, Twincast done to help increase nuke damage and your crit opportunity. Again, anything that will increase how fast you nuke, how much you crit for, how much base damage you do is all quite good for a mage.
This is just the way I would go for it. Basically we live and die with our pets, if our pet dies b/c he doesn't have defense AAs then we will die along with him. Then again we could run out of mana if you don't have enough DPS either so they can possibly go hand in hand. I would basically go hard defense for my pet then branch out into DPS for me and my pet. Seeing as you mainly just want the pet to sit there, hold aggro, and don't die while you kill the mob. I would also STRONGLY suggest maxing out Gift of Mana line of AAs quite fast (even if you don't have full defense max) it will end up saving you a lot of mana in the long run.
Another very useful AA for solo is Companion of Necessity. It can be used as a split tool or an oh smurf button. It blurrs up to 2 mobs after around 15 seconds of the mobs hitting it, re-useable every 10mins iirc. I would not suggest getting it rank 2 though, b/c like other mages have said on this board it basically will end up killing you more then saving you which is what we use it for.
Hope this helps.
