Give them both Midnight Oil (Geo) and the Bully talent. Easy access to +50% damage for all and reduces their AP and movement speed.
It can sometimes be annoying if it catches fire and creates smoke though, since you can't shoot them in smoke cover. (ie: it's better to use on their melee)
Save your talent point at 3 to use at lvl 5 (Glass Cannon). Boost Marksman to lvl 5 asap as well. You need the Quickdraw talent next (auto attacks only 3 AP then)
Learn the terrain and don't be afraid to run away. Proper positioning is key. Find better spots to engage instead of fighting on the enemies turf. Funnel them into right spots around corners, or cut of someone's path with fire/slow so it takes him longer to catch up while you fight the other enemies first.
There are a lot of options with attributes. You need decent Dex of course though more for requirements, I'd focus more on bringing up Speed to get max AP. And when fighting long range you need some Perception (increases hit by a lot).
If you want to cast some buff spells you need Intel as well, Wildfire is amazing, as well as Bless, the problem is that that you need around 7-8 Intel to have a 100% chance to cast it. Any lower and it's pretty annoying to miss during battle. However you'll always end up with some Int on your gear so you don't want to overdo putting full attribute points into Intelligence either..
It's a little tricky to find a perfect balance between min-maxing and "gameplay enjoyment" here. The same applies to Perception as well. You don't need 15 Perception (for the hit chance at least) but you can't leave it at 5 either. Lategame gear plays a big factor into the optimized equation.
Ranger is one of the few multi classes that really needs to spread attributes thin, while still gaining enough from it to benefit.
All in all, your combat revolves more on tactics with 2 Lone-Wolf Rangers. Which can be quite a lot of fun! You know... compared to simply parking your immortal 2h warrior next to enemies.