wrestling is used mostly for defensive purposes on a mage, it can be used offensivly but it's limited and will never do much damage. Disarm is defensive and stun punch is used to freeze someone for a second or two to get a spell off.
Tactics is needed for all specials EXCEPT wrestling, poisoning, and stealth. To use poison or stealth attacks you need weapon skill also, for example to use both specials on a dagger you do not need tactics, poison and stealth allow both of them to be used if you are 90+ fencing.
The main reason people use wrestling tho is so they can evade attacks, and for a mage it allows the use of a spellbook. A lot of mages also use mage weapons which are similar to wrestling in principle however requires a differnt set up. The mage weapon provides weapon skill equal to magery but usually has a negative penalty such as -20 magery skill, which can be offset by skill jewelry/items for magery. The easiest to explain is the staff of the magi, it is a spell channelling -0 magery skill, mace weapon. This means if you equip it you will have mace fighting skill = to magery providing "free" weapon skill for as long as the weapon is in you hand. In pvp it often gets disarmed thus negating any and all defense provided by it, and further strengthening wrestling. The reason people go for a -20 magery weapon is that it is 1 handed "defense" allowing the use of potions. A +15 magery ring and a +5 talismen or a Crystalline ring (+20 magery) will offset the penalty. The mage weapon is popular for tight skill templates.