Originally Posted by Jare
Speedloader is not a top priority. It only affects normal shots, which unless you have Gun Overdrive and can perform timed crits reliably, are always inferior to Power Shot, Double Shot, and Shooting Spree. Mind you, Power Shot, Double Shot, and Shooting Spree all have cooldowns that play off of each other (1.5, 3, 5-- you can literally rotate them infinitely without even trying).
Gun Booster is only useless if you've cashed out to the point where that extra damage isn't worth it. Mind you, not everyone does so the free extra damage helps. Logically it shouldn't since AC plays differently than the other main stats also if you read the description, it says that it is increasing Gun AP by 400. Balance-wise it should be %AC, realistically it is flat-AC.
Above average damage, below-average cooldown (average cooldown on AoEs is ~6-7 seconds, I calculated), above-average speed, not to mention the best kind of AoE targeting system in the game (the kind where you don't have to target). I'm not sure why you imply that everyone is ultra funded in your other two points but then somewhat imply that now no one's funded when you discus Shooting Spree. With 100 HV and 130 LK on my Lion, with his ultra out-dated gear, he never had problems using Shooting Spree. Of course, I did actually know how to play my character, so that could be a major difference as well.
"Two LK buffs backing you up" is deceptive because the total LK gain between the two is 63%. In most cases you'll be fine without having to compound LK or think about LK, but there are certain bosses, which if you aren't cashed out, will be a struggle for you. (And look! You're back to assuming everyone's cashed again!)
Gun Booster is useful if you are running around with a Rally Towel, an ultimate blue seal gun lv 5 with 600 AP and 12 AC, Ult. Brim cap with + 18 AC, GMV, poppuri leaf cape and baby lion as pet. Not assuming everyone is cashed, but they should be, unless you think you can clear chaos tower with that gear.
"Best kind of targeting AoE system in the game" if you want to be gang-banged by the monsters around you.
Shooting spree has an above-average cooldown time, you were right about this. I checked it out too. My mistake.
Power Shot > Double Shot > Shooting Spree is indeed a good combo but not for bosses. If you want to see a full damage combo on a single target, check my post above, it will also explain why speedloader is essential, not only for bosses but for fast quest item hunting as well. If you use your combo on a boss, shooting spree will hit the summons instead of the boss itself, you will lose a lot of time and damage and you will have a hard time for the rest of your life.
A gunner isn't all about skills. You have to know how to fully play your character(including timed criticals) in order to find out which combo is more suitable to the circumstances.