My characters archtype is also Fireblast/Thermal and im about to make level 30 and though i have a total of 6 more powers that i can take from here to 40, i only have 2 new ones that open up for me which are inferno, and prolly melt armor. Now I did not do a pure character that uses all of the powers that are available to it in its two power pool sets.
My style of game play calls for me to be a team player, and acquire powers that help the team/squad, which includes me staying on my feet and continuing the assult.
In the primary pool set
Flares
Fire Blast
Fire Ball
Rain of Fire
Fire Breath
Blaze
I can already take Aim, and Blazing bolt, but i opted not to take Aim primairly because i have a accuracy bonus in the Leadership tree
Assault - Bonus to damage
Tactics - Bonus to Accuracy (I think)
Manuevers - Bonus to defenses
Vengenece - Double bonus to all three, along with a heal
In the 2nd power set i have
Warmth
Fire Shield
Power of the Phoenix
Also thought it was important to take something to keep me on my feet, so i took fitness for the health regen and endurance regen.
Now considering i have 6 powers in the shute to still chose form and considering I am a team leader and team player. i want to devote certain power slots for the benefit of Fun(more damage) and other powers for the team.
Here is what i thought
for the remaining six powers
1. Blazing bolt... slot three damage and two accuracy, 1 damage
I want this for the sheer damage dealing im expecting it to do, and like you mentioned would be great to start an initial assualt.
2. Inferno- 3 damage 3 endurance reductions.. possiblynot sure.
Last ditch, in case we need it.
These two for the sheer damage dealing and my own gratification, that i am a damage dealer.
3. Heat exhaustion
4. Melt Armor.
I see these two powers as two powers to use for the benefit of the team, because if soften the targets for the melee and other attackers then its a team power, as well as does damage on it own, which makes me happy

.
5. Plasma Shield
6. Thaw
These two are essentially just for the team and dont benefit me except indirectly.
I bascially have hurdle for my travel power, besides im usually running with my SG and several of them have teleport, i can get there no problem.
What do you think of that template? Would u replace forge with something?