Once chosen your primairy and secondairy sets, you cannot change them anymore. You're stuck with en/fire.
Is that bad? True, there are better sets out there that do better or more damaging, but my EN/Ice was 1 of my most fun toons i've lvled to 50 so far.
You can combine melee PBAoE for teams (and tanker has full agro), along with the full set of energy for some nice damage. For solo, energy torrent is your bread and butter. It keeps mobs down and down = no dmg to you. Use burn for anti-melee counters (it fears the mob).
For 3:
While you been away they normalised all tier 1 and 2 powers, making them all cast at the same speed. For energy? Tier 1/2 became lovely fast to spam.
Also, old defiance (lower hp = more dmg) is gone. New defiance gives a certain dmg-boost per power activated, with a easy spam this can easily go up to 40-50% damage boost.
I'll look up my nrg/ice build, perhaps you can use the same but replace ice with fire powers.
50)Sinergy X/(50)Mika.
(50)MaceX/(50)Encore
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Heh, my first character, Blaster and 50 was Energy/Fire. Been such a long time since I've used it, mind, and I'm not sure if I wouldn't cringe at the build now.
From what I remember Energy/Fire's workable, not the best certainly, that in part being why I use my Fire/Mental more than Energy/Fire... it renders it obsolete in all fields. Quite horribly so, but that's saying more about the amazingness of Fire/Mental than anything bad about Energy/Fire.
Concerning Energy: Energy Torrent. Lovely power. Good damage, very fast to fire, EXTREMELY fast to recharge, long-range and wide cone. It will knock foes back, which while it might annoy teams if done uncontrolled, will when used well disable foes a few seconds, during which you could finish them with, say, Fire Sword Circle.
Alternative spin on that if you have Hover: get directly above mob, BU+Aim --> Energy Torrent to knock them down (rather than back), disable Hover and hit Fire Sword Circle as you hit the ground centre of them. Result, dead and maimed mobs.
As far as enhancements go, I would suggest for basic slotting of SOs, standard of 2 accuracy, 3 damage and 1 recharge for standard damage attacks. 3 recharge in Build Up and Aim. While in no way optimum, certainly more than adequate to be effective. A large part of playing an AT well is in what the player behind the character does just as much as what powers and enhancements they slot.
As far as must-have powers go, I'd say the following: Power Blast, Power Burst, Energy Torrent, Aim, Nova from Energy Blast. From /Fire: Build Up, Fire Sword Circle, Consume, possibly Fire Sword? I'd also recommend Hasten from the Speed pool for being a great power in general and getting your AoE big-hitters up and recharged faster, along with Build Up and Aim.
And regarding large changes: as well as the defiance changes listed in the post above mine, Blaster ranged damage across the board got boosted. 12.5% increase, I think.
In anycase, this might be somewhat a messy post. Rushed, and also, I really haven't used my Energy/Fire in a looong time, so my experience with both sets is distant.
Energy/Fire to me sounds like "chase and burn", which in all honesty sounds well fun 
If you are looking to play something different then here are some of the other powersets ive played and can vouch for:
Fire/EM (currently playing) - lost of self boost/buff with awesome seconday effects and great damage.
Fire/Mental - A LOT of AoE and good, fast damage. Decent secondary effects.
Ice/Dev - Caltrops > Trip Mine x 5-10 > Time Bomb > Tp Foe = Bliss. And awesome secondary effects from Ice
Fire/Elec - Very good on damage, and can self sustain endurance providing the target lasts long enough
Elec/EM - Has the best nuke in the game (imo), especially with Boost range and Power boost.
Archery/Fire - Total AoE Carnage. Nuff said.
Wow!
Thanks for all the great answers! I'll be sure to og 3 DMG, 2 ACC and 1 recharge enhancements on my ranged powers.
I'm gonna try out a lot of the stuff you mention, Amber. Seems like I haven't been way off track.
Hi there!
So the story is. I bought this game back in 05 and have been slowly, but surely, leveled my EN/Fire Blaster to 34 over, mainly, the first two years. Other things occured (read: WoW). Anyways. I have a really hard time speccing and figuring out enhancements. Tbh, I never really got into it and just used/pressed randomly.
So, I have a few questions that might make it easier for me to get back into CoH:
1. I'm an EN/Fire Blaster. Is that any good? Can I... change powers?
2. I really need a spec for this Blaster. So far I've just taken about any power and some random enhancementslots and just used the enhancements I had laying around. Does anyone got a clue on how to get me on the right track? I'd like a build that's also good for soloing (as I've never been able to do so before).
3. Has there been anything else or major changes from, oh say, 06/07 that I should know about?
Anyways. Any answers to these quite big questions will be deeply appreciated!
- Tox