Nostalrius Begins - Quality wow vanilla realm (1.12)

Hi I am currently using rivenspike and frostbite. I have always been told to put the slower weapon in the mainhand but in my situation my faster weapon is actually stronger. Does that mean i should put frostbite in my main hand? Also would putting rivenspike in my MH increase the chances of it to proc the armor debuff?

Rivenspike Mainhand for longer Fights. Otherwise use Frostbite, cuz of the higher MAX DMG.