Rangers.... what are they good for:
Pvp: decent enough (unless you are pking, better classes for that).
Oad: Not enough DPS and their pets while statistically superior to golem/zombie are outmatched due to how easy golem/zombie are replaced (also sorcy/necro are on a par/better with dps and bring other abilities). Once the ranger goes through its 3 pets it will take at least 2 rounds to get one back (1 attack to revive, 1 attack to summon and about 6 attacks to heal up), whereas a sorcy/necro takes 1 attack.
Pve: decent enough (levelling is easy because things are not going to kill your pet unless you totally neglect it) for farming, there are better classes (low dps and a pet will not make that substantially better).
RP: Any class/race/stat combo is suitable for this, the player is the important part here

Suggestion to make rangers more useful:
Allow pets to be revived and re-summoned with one attack and have them begin with a % of their health based on CHR (cheers Snyper, CHR makes more sense than just a %).
Other possibility you can revive using extra attacks to increase how much HP it comes back with (based on 22 CHR? 1 attack = 25% health, 2 attacks is 50% health etc).
Ranger Scrolls/Taming:
I have not used a ranger scroll myself, but I believe that it shows the level, div, race and if tameable? Taming a pet can be extremely tedious and to start with you have no idea if what you are taming is any good (esp. since the ranger scrolls show such little information).
The chance to tame at CHR 20 = 4 or 5% at equal level.
You waste a lot of time and effort (unless you are lucky...) trying to tame a creature and find out (when you finally nail it)... that this level 24 beasty is not any better than the level 5 critter you already have. Yay. Can you be bothered trying again with another higher level creature?
Basically this is not a fun mechanic, unless you have a general idea of what you are getting for your time and effort.
Suggestion to make the taming process better:
Have the rangers scrolls show you the average stats of the creature you use it on, basically the info that you would get from having just captured a creature and examining the soul gem except that it will be the average for the species you used it on and not the actual creature you used it on, in other words you see the base stats of an average Crow and not the stats of crow #2212).
using a ranger scroll on something that is not tameable will only show you Race, Div, Level.
What do ye'all think?