i have macros to imbue my offhand with every enchant. i can post it later, not on my pc atm, but you can google it fairly easily. i play frostbrand vs wizards when i know im going to get kited, and swap to frostbrand to sprint away from melee with cooldowns. also swap frostbrand to connect for swaps. flametongue primarily vs cleaves and when you know you will have ~15 seconds of uptime. its about 5% more damage in my experience, not that i tested it much. the passive frostbrand slow doesnt really matter either. if you're playing enh you're playing a cleave and your teamate probably has a passive slow that doesnt reduce their damage throughput
yes, flame shock. subtract flameshock from your rotation whenever you are bursting. its shit damage really but it adds to your sustained damage in the end. a crit earth shock isnt exactly insane but it beats screaming at your teammate to do more damage for you to get a kill.