Soloing is possible at the lower levels, especially with the help of the newbie buffs that have been added to make it a little easier, but you'll need the support of a group after reaching the mid-levels of the game.
Another thing that makes progress in Lineage 2 seem slow is that weapons are expensive. You'll want to stick with the same one for quite a few levels simply because you can't afford an upgrade. It helps to gather the raw materials and seek out the services of a Dwarf, although this is still a lengthy process.
Most of the quests, at least at the lower levels, require considerable grinding for pretty meager rewards. Rarely do you get any experience points for completing a quest, so they don't really serve as alternatives to killing the same monsters over and over again. It's not uncommon to come across a quest that asks you to collect 100 items dropped by a particular mob.
I also came across some dungeon crawls, but they were persistent areas with respawning monsters like the rest of the world, which is a switch from the instanced approach used by so many MMORPGs these days.
There have been improvements to the quest system since the game's release. For example, NPCs with appropriate quests for your level now have a telltale yellow exclamation mark over their heads. Unfortunately, the quests I came across left a lot to be desired, and they didn't do much to draw me into the game.
Unlike most MMORPGs, there are no restrictions on who may attack whom in Lineage 2. Typically this would make it difficult for new players to progress through the game, but Lineage 2 uses a Karma system to discourge indiscrimate player killing. If you attack another player outside a siege or guild war, you take a Karma penalty. Bad Karma allows other players to kill you with no Karma penality, and makes various NPCs hostile toward you. To work off your Karma penalty you have to go back to killing monsters.
This system works remarkably well. Ganking certainly does occur, but it's dramatically less frequent than in games that don't enforce any penalty for it.
One interesting aspect of this system is that you can't see what level other players are. You have to judge them solely on their appearance, which can be very deceiving if a high-level character decides to equip low-level gear.
Battling for Glory
Guild vs. guild combat for control of the castles in the world is a central feature of Lineage 2, but it's hard to get involved until you reach the game's higher levels. I have been able, however, to take in a few sieges by various means, including the in-game Broadcasting Towers, which allow you to watch sieges without participating.
Sieges are scheduled for certain times on weekends, and they last 2 hours. Guilds of at least rank 4 on the defending and attacking sides register in advance, with the winning side taking control of the castle, and the financial benefits that come with it, for 2 weeks. As you can imagine, there is a lot of politics and diplomacy surrounding sieges, as a trustworthy ally may make the difference between winning and losing.
The scale of these events is impressive, and they are plainly one of the game's most compelling features. I would encourage new players to use the Broadcasting Towers to get an idea how these play out, because after seeing them you may decide that it's worth grinding levels to get there.
It's a little disappointing that they only occur on weekends, and there is really nothing keeping the two sides balanced in numbers. Getting a good turnout is important.
Nevertheless, this is the sort of massive persistent-world battle that a lot of PvP fans crave, few games offer, and even fewer games can actually implement from a technical standpoint.
Given the stuttering you get when you run into a town, I expected sieges involving hundreds of players to be very laggy. After running into one in progress, I was surprized to find that, once the initial loading is over, they are relatively smooth and quite playable. The game engine definitely handles large numbers of players better than most.
There could be some superb end-game content in Lineage 2, but I'm afraid that a lot of players, myself included, aren't likely to make it that far. If I have to play a game for months before I'm able to partake in any really compelling features, I tend to lose interest, although some people don't mind putting in the time, and even prefer a game that is demanding in this regard. The guild system and castle sieges do have promise, and they are significantly different from what other games have to offer. For those that find other MMORPGs too easy, or lacking in large-scale PvP battles, Lineage 2 might be a perfect fit.