I just started rebel also so I am still experimenting.
1) If you're looking to do auto attack Gatling, it would be better in a controlled environment yes. You will most likely need to wear elemental armor + HP pot. The biggest issue with Rebel is that it heavily relies on buffs to make it effective. It's a hard class to MVP since it has very low HP pool, and if you die you need like 10 seconds to recast and rebuffs everything. Im not even sure if it's worth pumping points into VIT right now in PVM because you will be one shotted by any mid or high tier MVP regardless. Anyways a good alternative after dying is to switch to pistol build after you got ress, since you probably just need to recast hit barrell, eat some pots, and go back to action.
2) My slug shot does more damage than the grenade launcher and Hammer of God. I heard somewhere people get to 1m damage per shot with slug, need to test that though. I would say 150-300k is more realistic number =). The hit rate would be an issue but I think you can still hit low tier boss on gears and buffs.
3) Rifle build is more for PvP / WoE in my opinion. Hammer of God horrendous cast time and extremely long after cast delay alone will probably deter you from using it lol. Also it's hard to get 193 aspd using rifle, the best rifle rebel have auto cast decrease agi on wearer every time you attack.
4) I heard the grenade launcher is a good alternative to slugshot build for MvP. I will need to test that also. The bigest issue is probably you need to cast Crimson Mark debuff on the target before you can use the skill.
5) I would personally go for maximum 125 DEX because dex is used directly in some of the skills formula such as round trip. 110 AGI is plenty for 193 aspd and the rest can go to LUK for extra damage and VIT for HP pool / stun resistence. You can also add 30 INT for a bit more SP pool, but I personally just pot that through. Be sure to always carry some green pot especially with 1 INT though.
Rebel is a great class to level your leeching alts lol. From 99-125 is really a cake walk, you just round trip your way to high TI with ease. Rebel is super weak against range and magic users, so always avoid those when leveling. After 125+ it starts t become a challenge since Rebel don't have access to end-game gears like Rangers do. So your round trip are stuck at 40-50k damage and enemies usually have over 100k HP.
For MvP, it's not really viable to solo mid to high end MVP due to its HP pool. The damage output is poor comparing to well geared and no limit ranger. They really need to sell 500ATK vendor gears =). You can play around with binding trap but the MvP will pretyt much one shot you with any skills in its arsenal.
After 130+ Rebel role becomes more similar to Gunslinger, a squishy range debuffer. Binding traps and grenade launcher can be very useful there. I am trying to see if it's viable in WoE once you hit max level. I could see it being used to snipe out SD mech or push suras and everything else away from your team with Round trip. Just my two cents.
It's really sad renewal made few classes so powerful that it overshadow every other class and ruin thesynergy. It used to be where very class has its specific use. Hunter, Knight, Wizard, Blacksmith, and Priest days I am referring to =)
