I like this game, but when I play with my friends we always have to sit someone out. My suggestion is to add another party slot for a fourth player, as well as a ranger class. Ranger class can have spells such as entangle which are already in game to slow down enemies. Ranger's attacks would have a minimum of two range, up to four or six range with bow, crossbow, or net attacks. Primary emphasis is on four player support though. My friends and I like playing CH, but it's lame that 1/4 of us can't join in and play. Bump the three player parties up by one.
I can immediately say that the new class idea is not going to happen. From what I've found from looking around the forums, the devs are not interested in adding new classes as it would create major balance issues. Also, if they haven't added a class all this while, I don't think they will do it now. About four players, I don't know what to say. It could create balancing problems as well. Levels that were meant for three characters now become extremely easy to complete. Sorry to shoot you down, it's just I think it would be too much trouble to go into.
I don't suspect it happening in the campaign... But there are some MMs that 4 could co-op. Better yet jump over to multiplayer and y'all can battle each other in 2v2 teams using the custom game feature.
You can also make your own maps that pit 2 on 2 or 4 versus the computer. I've made a three part campaign that you can play with four people entitled the fearsome foursome: http://forums.cardhunter.com/threads/mauve-manticore-submission-thread.4544/page-12 You would need to download the scenario, Invite all three other players to your team, Create a Casual Game, Custom, Load Scenario, then click play. Also, if you haven't realized it yet, the priest is the ranger. Look at all the ranged stuff he's got: entangling roots, rad. bolt, rad. bomb, rad. spray, rad. goo. Each of the races have a ranged spell or two as well: dwarves have War Cry, elves have Scouting Run, and humans have Jump, Soldier!. Either that or you could turn your mage into a melee monster and call him a ranger too.
You don't need to mention every single rad card on priest for us to the idea and your list only includes entangling roots and rad attack and terrain series which isn't much. Radioactive attacks aren't the type of thing you would expect from rangers. You gotta be kidding me. While you are technically correct incorrect (actually some of those are projectiles not magic), those don't do any damage and aren't really in line of what you would expect from a ranger. You are correct that mages are similar to rangers except they don't have similar tech.
No real value in being a "Grumpy Gus" to a suggestion that is just trying to help. Whether you're using a very strict, or super loose definition of ranger, since it's highly unlikely that a 4th class is coming anytime in the foreseeable future, Tolkien's thoughts on the topic could still be helpful to a newer player looking for ranger-esq options. Let's go for a little less 'Melvin,' and a bit more 'Gary.'