Control - In particular mesmerize (think silence on steroids), and forced targeting
Game Breaker - Not as much as she used to, but still pretty potent.
Tasty - Spider likes her a lot
Reverent - Angel Dragon is able to bring her back
Magic attack and skills
Mesmerize - Oh boy this white is really good. First off it damages everyone, not amazing but appreciated at any time. Then it inflicts the "unique" mesmerize ailment on all enemies. Mesmerize blocks active skills, and punishes foes for using them by draining their energy anyway. The best part? It bypasses tenacity so it's pretty much guaranteed to work. This skill alone made her mandatory on teams for a long time.
Feral Taunt - This is an interesting control skill. Basically it makes it so that all attacks go to the ally with the most HP for 6 seconds. This includes area of effect (they will only target the one hero). It also gives a strong armor boost to help mitigate everything. This is a great skill to pair with a strong tank to keep the rest of your party safe no matter what.
Call of the Wild - Spirit Wolf's official damage skill. She just does magic damage to the nearest enemy. Nothing fancy. It does have piercing attached to it, so it's buffed by shadow assassin if you're running her as well.
Critical Thinking - Boosts everyone's crit rating. This boosts everyone's chance to land a critical hit. Always welcome regardless of team makeup, since everyone like more crits.
The Next Day You're Out - A somewhat odd (but not unwelcome) addition to her kit. This make debuffs stronger and gives her magic vamp. Magic vamp is great since all of her attacks are magical, meaning that she will regain health with each hit. Spirit Wolf has no inherent debuffs, but some other characters appreciate the boost.
Spirit Wolf mainly wants expertise, which is not attached to a rune family. I would recommend river or bolt to boost her energy gain and let her fire off that wonderful white skill more often. Beyond that, it's pretty much whatever you like. She really only needs a handful of stats to break everything, and the rest of just a bonus.
Like Moon Drake, Wolf can fit on nearly any team and do well. However, the following categories of characters probably appreciate her the most:
Off Tanks - High HP characters that maybe aren't inherent tanks on their own, or tanks that are lower on the armor ranking scale (Dark Dracul for example)
Crit Fishermen - Characters that get bonuses for getting a critical hit or have their own critical hit increase (Rabid Dragon)
Debuffers - Charcters that debuff foes get a strong boost from her legendary (Kraken King, Frost Giant, etc.)
Karaoke King - The character that took her throne is also the one best equipped to take her down. With a faster shutdown skill and immunity to magic, Wolf doesn't stand a chance.
Dwarven Archer - Archer doesn't care if her active gets shut down and she hits everyone with physical attacks.
Ninja Dwarf - Attacks high intelligence heroes, Wolf is a high intelligence hero.
Ancient Idol - Idol's swap draws from the rear of the party...exactly where Wolf usually sits. This makes her a sitting duck.
Ambush Spider - She tasty.
Spikey Dragon - Targeting the rear with strong physical attacks, hitting Wolf often.
Rabid Dragon - If he can get his white off she's pretty much dead instantly.
(+) Game breakingly useful white skill
(+) Able to silence pretty much everyone, can even start a match firing that off with enough starting energy
(+) Has magic vamp and all magical attacks
(+) Provides crit boosts to all party members
(+) Feral Taunt keeps AoE effects from hitting the party and protects weaker party members
(-) Mage level defenses
(-) Bad damage