Tough is one of those traits that's really hard to make work unless you've already got some. Yes tough-2 is good but it's way better at -4 or -6. The only mages that realty get to flex the"tough-" muscle at all are the Anvil throne warlord who comes with tough- 2 and the beastmasters who, with animal kinships can stack tough to- 4or-6 easily. Anyone else who has no other way of applying a stack of tough beyond the colossus belts -2.
That having been said tough is a pretty great trait if you want to stack it with elemental -# that come from various chest armors or the elemental cloak. The colossus belt and Chitin armor from octgn promos nets you effectively acid- 5 on the effect die which is huge! Acid ball goes from 100% effective for one corrode to a little under 60% for one corrode. Not to shabby. Again though that belts usefulness is limited and with the other belts available i honestly don't see very many colossus belts being played. Just my 2 cents