Just to convert the last hold outs over to the dark side of COH (maniacal cackle) here is an updated version of my original L30 in 2 weeks guide. This guide provides a Fire/Devices build and schedule through L41 and a levelling guide to achieve L41 in four weeks. It's based on 4 hours a day play time, 5 days a week (or 20 hours a week broken up anyway you want). Keep in mind that this build is geared directly for levelling fast (solo and group) and not particularly for missions and/or TFs, although by L32, you will have achieved a build that is suitable for any occasion, except maybe the AT pity parties that this build will engender
I've found that most every build by and large works out the same in the end (i.e. an eng/eng Blaster is virtually the same as the next eng/eng Blaster at L50). The trick to character building in COH seems more to do with scheduling your powers and enhancements rather than what you actually pick (unless of course you're desperately trying to gimp yourself).
Build - Fire/Devices Blaster (* indicates notes at the bottom of this post)
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L1 - Web Grendade (accuracy), Flares (damage)*
L2 - Fireblast (dmg)
L3 - 2 slot Fireblast (dmg)
L4 - Fireball (dmg)
L5 - 2 slot Fireball (dmg)
L6 - Caltrops (slow)
L7 - 1 slot Caltrops (slow)*, 1 slot Fireball (dmg)
L8 - Flame Breath (dmg)
L9 - 2 Slot Flame Breath (dmg)
L10 - Targetting Drone (tohit buff)
L11 - 2 Slot Fireball (6 slots now (dmg))
L12 - Hasten (timer)
L13 - 1 Slot Fireblast (dmg), 1 slot Flame Breath (dmg)
L14 - Super Speed (end reduction)
L15 - 2 Slot Flame Breath (6 slots now (dmg))
L16 - Smoke Grenade (tohit debuff)
L17 - 2 slot Fire Blast (6 slots now (dmg))
L18 - Hurdle (jump)
L19 - 2 Slot Hasten (timer)
L20 - Health (health)
L21 - 2 Slot Hasten (timer)
L22 - Stamina (end recovery)
L23 - 2 slot Stamina (end rec)
L24 - Aim (timer)
L25 - 2 Slot Stamina (end rec)
L26 - Blaze (dmg)
L27 - 1 slot Stamina (end rec), 1 slot Hasten (timer)
L28 - Trip Mine (dmg)
L29 - 2 Slot Blaze (dmg)
L30 - Cloaking Device (end red)
L31 - 1 slot Smoke Grendade (tohit debuff), 2 slots Targ. Drone (tohit buff)
L32 - Inferno (dmg)
L33 - 2 slot Blaze (dmg), 1 slot Trip Mine (dmg)
L34 - 3 slot Trip Mine (1 dmg, 2 timers)
L35 - Blazing Bolt (dmg)
L36 - 1 slot Trip Mine (dmg), 2 slot Inferno (dmg)
L37 - 3 slot Inferno (2 dmg, 1 timer)
L38 - Hover (end red)
L39 - 3 slot Blazing Bolt (dmg)
L40 - 2 slot Blazing Bolt (1 interrupt timer, 1 dmg)
L41 - Flight (end red or flight speed to suit)
* You choose Flares because it's a great tool in the 1-20 levelling when it's damage isn't as minor comparatively. After 20th level you will use this rarely if ever. In the future, when Respec is available, I would respec out of Flares later (although I've found Flares actually useful later on as well). Rain of Fire is specifically counter productive to levelling this particular build. Caltrops (currently) 2 slotted provides just enough slowing to make 1-20 mobs stick together (even though they are trying to scatter). 1 slot they move too fast, and 3 slotted is a waste of a slot later on (as you hit the slow cap with 2 SOs ... also you use this much more rarely post 20th). I don't emphasize Hasten until around the time you're getting Stamina. Without Stamina, Hasten is good for a splurge and a bunch of down time (however it will allow you to take higher cons then you normally would by 1 con factor).
Levelling Guide
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L1-8: Solo street stuff. It should take you about 3 hours to hit L8. I prefer Galaxy City as a starting point (better Tram placement and training location to parts of the zone) but either that or AP will suffice well enough. At L7 you will want to hit the Sewer Network and/or Kings Row).
L9-12: Perez Park. You are specifically looking for gaggles of blues and greens here. Why those? Because you will be able to 2-shot them with Flame Breath / Fireball combo. Then run like hell and pick off those stragglers. You will kill much faster then trying even cons or better (hence the XP will come in faster which is the whole point of this build). EXP Rate: 1 level per hour.
L13-20: Boomtown. Start at the front of the zone AOEing gaggles of Trolls. Proceed on to 5th Column in the middle of the zone in the 14-16 range. Then on to north Boomtown and The Lost. You will also see a lot of Clockwork here. The Lost go down much faster and tend to spawn in tighter packs (always a good thing for AOErs). Blues-Whites are best throughout your Boomtown experience (greens for L13-14 will work as well). EXP Rate: 1 level per 1.5 hours.
L21-25: Dark Astoria. Start at the right hand side of the zone (west end). Super speed around and 2-shot gaggles of blues-yellow cons and super speed on to the next pack. Don't worry about stragglers or LTs left standing as you will get experience when another group comes along and cleans up your mess. Use Smoke Grenade to keep safe while doing this. Don't use it to speed up the levelling a bit (but you will have to keep a much sharper eye on your health and situation). EXP Rate: 1 level per 2 hours.
L26-30: Terra Volta: Start at the right of the zone in and concentrate on packs of Sky Raider Captains (LTs). These give amazing XP compared to minions and you can 2-shot blue cons (whites and yellows with Aim). Stay way from Freak LTs and Bosses. In TV you will want to actually kill all of the packs, rather then 2-shotting and moving on (LTs are juicy XP so everyone is worth the time and effort). EXP Rate: 1 level per 1.5-2 hours.
L31-33: Founders Falls, front of zone (waterline docks left of zone in) 5th Cols. Vamps are no problem with Smoke Grenade (their mezzes still need to hit to stick) and those same Vamps scare most other soloers away so the area is pretty clear of people usually.
L34-35: In a trio group, the NW corner of Crey's Folly is the best XP hands down (Freaks). Solo, I would suggest COT Avenue in Founders Falls (red river sub-zone). It will *seem* slow (primarily because it's boring as hell) but it's actually great XP if you check it against your watch. You have two sides to choose from so one is usually not camped and each side can easily support a pair of soloers/groups.
L36-38: Abandoned Sewer Network (zone into Sewer Network at Steel Canyon, immediately turn right and go through closed door to Abandoned Sewers). You will be fighting Hydra spawns (mixed mins, LTs and Bosses).
L39-41: Peregrine Island docks. Be prepared for everyone to scream at you on your first couple of trips while you learn the ins and outs of the area
Bang 41. This assumes selling only at the end of a levelling session which means you will most likely have to farm for a couple of hours over the course of this build to pay for your DOs and SOs. This build also assumes that you are in DOs at L12 and SOs at L22. If you have an L30+ friend or character of your own, fund your Fire/Dev Blaster that way.
One of the neat perks of this build is that you can help friends power level like mad (and your Tanker/Controller/Defender friends will love you for this). You can also duo/trip with just about any combination of ATs for great XP. At various points in this build, grouping will be desireable over soloing for XP gain. Specifically in the mid 30s in Crey's Folly but at other points as well depending on how "balls to the walls" you like to play.
This guide was made and updated as of 8/20/04 (before Content Issue #2) and I will attempt to keep it updated as possible through the inevitable changes that are sure to come.