You make some good points with your build but you miss you real opportunities. These are in no certain order.
M30 Gernade - ok, it does scatter KB. However, Build Up + Shotgun + M30 Gernade = Dead Blue Minion Spawn and below (and this is with training origin accuracies slotted out... I dont touch damage until DOs arrive). This will allow you to blow your way to flamethrower by sweeping Hazard Zones. Do you keep it is another matter entirely. If you respec in the later game then drop it, but it will still serve you as a last damage push after dropping the seriers of AoE Cones. I also love it as a panic button in emergency situations. You (or your team) is in retrograde operations (retreat), drop a gernade in the enemies lap. The scatter knockback will sew a little chaos in the enemies at you beat feet. M30 Gernade + Boost Range = completely safe AoE Damage. It is also useful in a bad pull, just find a corner. 1st enemy sticks his head out around the corner and BAM!, all his friends running close behind all get hit for the AoE too. Now you sweep around the corner and rain death on them with the cones while they are trying to pick themselves up off the pavement. If all you want is cone attacks then this does not fit the build. If you want to put as much damage as possible downrange toward a target(s), I would rate this higher than a "2".
Power Boost - oh is this a great power. All I have to say is get the Medicine Pool and use Power Boost. +100% to Stimulat, Aid Other or Aid Self is just to nice to pass up. As an AoE Blaster your three biggest concerns are Endurance, Health and Aggro. You can manage the Endurance with Conserver Power and Stamina. Power Boost + Aid Self will help manage the Health. If you hit them with all the AoEs you won't have to worry about the aggro, dead men don't shoot back. This deserves at least a "3" in the usefulness scale. It earns its pay with Power Thrust, Bone Smasher, Stun, Total Focus and Beanbag. The Medicine pool is just gravy.
Burst - why take it? If you put 2 recharges in Slug it will be back up almost as often as you need it. If you went SuperSpeed and have Haste slotted, then it will be up as often as you need it (unless your need is a semiauto slug power). If you want single target damage hit em with slug or pop em with Bone Smasher/Power Thrust (and that is in the lower levels). Personally I would rather lay the hammer down on the whole group then pull one by one (we are AoE damage dealers here, we want the spawn not just Fred or Barney). Giving Burst more than a "2" is a disservice to the rating scale.
Unconventional Tactics (ie not the Cones/AoE)
Beanbag + Stun does lock down a boss. Power Boost + Bean Bag + Stun = doing whatever you darn well want to a boss. Drop Bone Smasher and/or Total Focus in the mix and the boss will probably never look at you ugly again.
Stun/BeanBag on a LT or below followed by Bone Smasher and Power Thrust is a stunned LT way over there about to get a Slug dropped into his chest.
Now, I know we are all about the AoEs but sometimes you want take someone out of the action fast. Tsoo Sorcerers, Sappers, you get the picture... you dont want them doing what they do best. Boost Range + Beanbag (if you cant kill them outright with a Boost Range + Snipe + Slug) will draw the lower level threats to you and leave the uber threats far behind the front line action. You can then take them out at your leisure.
You have a great guide, I think you just need to look a little beyond the Cones.
