I know, i know, most people are going to tell me that the rangers aren't good but im going to be doing it anyway...
I have to disagree with those people, especially with lone wolf a ranger will be completely ridiculous.
There currently is a topic on how to build a ranger, I coincidentally have replied there with with my point of view just a few days ago.
http://www.larian.com/forums/ubbthreads.php?ubb=showflat&Number=539712#Post539712Now with regards to your main concern/question: I personally think that even on hard you can complete the game with 2 lonewolves which are not directly spellcasters, on the other two difficulties you could probably even complete the game with just 1 character if that was an option.
If I may offer some advice, I would refrain from spending points into weapon skills (other then tenebrium), later in the game they become kinda obsolete. So that means don't limit yourself to just one weapon type. Also with non casters it becomes more important to have a decent stash of usefull scrolls and this means buying scrolls will be somehwat of a goldsink.
A few examples are: oath of desecration, drain willpower, teleportation, featherfall, (elemental) shield, absorb the elements, summons, and for your melee type of fighter find/buy lightningstrike scrolls. It gets him into melee, it deals damage has a 30% chance to stun (more if characters are wet) and it can be a setup for dust devil/whirlwind or flurry etc.
With kind regards,
Rashar.