Magma Totem in a dps rotation for enhancement adds a substantial amount of dps. You have to remember that the SP bonus from Flametongue isn't a flat damage increase. Most of the spells being used by other casters receive only a percentage of their SP converted to actual damage on their offensive spells. The same goes for healing. So if you're talking about say...a 50% scaling on a particular spell for spell damage, take the Flametongue Totem, divide the SP buff by 2, and that's how much additional damage you're adding for the raid every time that person casts that spell. Most raids aren't going to have more than 7-8 offensive casters. But to keep it simple, assume that you've got 8 casters in a 25-man raid gaining 100% benefit from your FT totem. It's still going to work out to less damage than your Magma Totem will provide.
It used to be that shaman totems were considered group property. You dropped what the group needed (ie. back when Windfury Totem produced the same effect for the melee in your party as the Windfury imbues we had for our own weapons, it was still expected that you'd drop that in a melee heavy group even though it did absolutely nothing for us). Now we buff ourselves first with passing consideration to what that does for the rest of the group. There are exceptions, but barring an extremely caster heavy 25-man raid Magma Totem is still bringing more to the group than FT.