Rashemi Elemental Summoning is awesome, though Conjure Ice Beast does diminish the benefit of the Thommil's Engulf ability, though not entirely (engulf some foes, earth glide down into the ground... they go with the elemental and never come back...)
But each summoning of an Orglash gives you 3 castings of Cone of Cold (at their HD for CL) for "free." Summon several of them, have them whirlwind and trap some foes, and then cone of cold each other (and the foes within them). One fifth level spell can get you three 8th-caster-level Cones of Cold; one sixth level spell gets you three 16th level Cones of Cold.
Sure, it's somewhat situational, and it's "blasting," which we all know tends to be sub-par, but you're actually getting a decent return on your spell slot investment (45d6 damage over 3 rounds for a 6th level spell, save for half), and two rounds' worth of casting it were "free" actions on your part.
And remember that Thommil can be added to things like a Thoqqua, which also does fire damage. I was always so sad there was no way to summon the paraelementals from the MotP (a Magma Thommil would have been HOT!)