Your build looks like the bottom half of a good early raider's build, however you're missing out on a very important part of being an Affliction Lock.
Bridging level 40 essentially brings new life into the Affliction Drain-Tank's abilities, and really opens up 5-man gameplay with a key new Spell: Dark Pact.
Keeping your Imp out, phased out with Fire Shield turned off, you have yourself a new steady source of mana.
Your best bet for damage in 5-mans still will be SBolts, yes, but you'll find yourself needing to sit and eat/drink without a source of mana, and unlike organized Raiding, 5-man healers usually don't feel like healing Life Taps.
Having tried a build similar to yours for a while, I will say you'll see better returns off the SBolts you cast, but you wont be able to cast nearly as many of them. Past that, SBolt spam doesn't make a good grinding option in comparison to Drain Tanking, meaning that you'll be gimping your solo play to give a theoretical boost in 5-man damage output which you wont really need - you may infact find yourself pulling too much threat.
Stick with Dark Pact, it's amazing.