Not really as swapping from tg to smf incurs a 30 second internal CD so you will not get the 35% damage increase from smf for those 30 seconds. It might work out if the mechanics allowed a long execute phase via cut scene etc. but overall Blizzard out this internal cd in the game to prevent warrior from doing exactly what you are suggesting. On the right fight with a bit of planning it might pay off but overall it would most likely be a dps loss.
The only fights I can think of where this might be beneficial is Elegon and Blade Lord Ta'yak. On Elegon you can switch during the last pillar phase and probably be passed the icd by the time you get back onto the platform, at which point he should be closing in on the 20% mark. On Blade Lord there is at least 20 seconds, and in most cases probably more than 30, where you're doing absolutely no damage during the transition which makes a switch perfect. If I had better 2handers and could be bothered to properly enchant them, I would definitely try it out on these bosses.