Speaking from limited experience playing a white lion up to level 15 as well as playing alongside them in scenarios, I can give you a rundown of how they play.
You will find the White Lion to be a formidable character throughout the levels. Unlike the Witch Hunter, who starts off strong, then has a weakling phase, and then becomes super powerful again, the White Lion consistently plows through enemies and only gets better at it with levels. In Tier 4, a WL can dps down so many things in mere seconds.
Like all melee dps however, they are forced into very dangerous areas of the battle and are high priority targets to take down. A WL will go down really fast when focused fired. Expect to die a lot if you don't have good healers helping out. Some people hate the responsiveness of the lion but I have found it to be able to switch targets and manage it fine once I reassigned some of the pet hotkeys.
As a healer, I've noticed quite a few suicidal WL players. It is an 'ok' play style and some love it but in order for it to be successful, a WL would need to be rezzed because if the other side is rezzing more, the suicide means nothing. But its just that their dps is so insane, players like to see their foes drop in a few axe swings.
If you are good with war tactics on the battlefield, you will find the WL to be very enjoyable. For example, sending the WL in CC mode to snare healers, or damage mode to help you smack down something. I would frequently recall and heal my lion if I let him fight on his own for a dozen seconds or so. Many people dont manage it that much. I find trying to keep the lion alive for more dps is a big part of my WL play.
Later on, you get a super pounce ability that basically flings your character in the air and then smash down on your enemy. You also have an option to fight without the Lion (called the loner build). An old guild member has commented somewhere on this board about it.
In terms of points allocation, I don't have many recommendations. The general feeling I've had is to either build up your str and coordination tactics with the lion or to pump up the points into the lion's skill tree and send it around terrorizing destro.
You don't get a lot of group utility although they have a group damage buff that seems to not get used by players enough and I wish they did.
If melee dps and glass cannons are your thing, than a WL will be fun!
