1: yes, more so if working in groups.
2: Karma system affects how much loot you drop on death, if you are a criminal or a sheriff, time spent in prison (or size of bail) if a sheriff kills you (a criminal), no stat loss, no rogue state. Some towns may be pvp friendly allowing criminals to use the the towns crafting stations, while the default is that you cant. However if you are a citizen or resident of the town, at which point your karma is irrelevant for that purpose.
The justice system punishes criminals by them getting locked into prison for up to 48 real world hours or having to pay 10k? -I am not sure- to be released. Note that when you are released you only have the equipment that did not drop on death (and if you are criminal, all of it does), and you are released inside the town that built the prison (hostile territory). Oh and you can only pay the bail yourself if you have that much in the global wallet, which can only be added to via a bank or market when someone buys what you put up for sale. Otherwise your friend has to travel to the town and bail you out in person.
Simple attrition will destroy the marauding gank squad, limit them to regions with criminal towns, or make the act unprofitable without significant investment in gear/skills/talents.
The amount of loot a character can carry is very limited, thus requiring the building and use of town banks or private homes and chests. You are limited to one house plot per account. This means having to transport your loot to a drop point safely. If it becomes known the plot is used as a bolt hole for criminals you can bet it will get the attention of the sheriffs. This means having to transport your loot to a drop point safely while under pressure.
Town banks are only accessible by criminal players if the town is criminal friendly... presumably rare...Or you are a citizen of the town. Town leaders are probably going to be picky on who to allow citizenship, especially as it is not necessary.
The starting skills are not anything to sneeze at but are certainly not competitive. It would take a weekend to get the skills for a modest build and there could still be weaknesses. Not to mention that equipment is a major component of any human build.
The horizontal progression is not quick. Unless you have some outside feeder source, it takes well over 40 hours to get the equipment necessary to be effective. Not to mention that skills and talents can easily take longer and are not transferable between characters on the same account. Groups help, but there are also AOE powers (only really obtainable through moderate work) and a person in a -good- build can take on 3 with shitty '2 hr builds'.
Due to equipment decay, no repair, and a constant flow of goods, the griefer groups will not be able to make any lasting damage to the players they victimize and bring lots of attention to them from the sheriffs.
The fact that there is very limited fast travel (from port to port) which is also expensive also greatly reduces the affect and range of griefers. Even at its worst two alphas ago, the cry of 'reds at XXXXX' would see anyone feeling vulnerable in that area log off and on to an alt elsewhere, while all near by sheriffs converged like hunting dogs for the kill, chase, or to patrol incase the reds came back. The griefing was also heavily localized to 1/4 of the island area. I myself lost three sets of gear to griefers, but it barely set me back at all since I had the economic weight of a week of materials generated by my guild and town, and I know that two of those times the griefers were hunted down by eager sheriffs. Being grieffed was more of a -sigh- event than a rage quit one. In the last two weeks of that test griefing was practically unheard of as was the case of practically the whole of the last alpha. -to my knowledge-
While there are many ways a grifer could use alts to avoid the pain of prison, it would still be a massive amount of time spent -not- progressing. In the world of the red queens race (better equipment synergy, skill sets, talent synergy, group cohesion), you would just loose in the end.
It is totally possible that an organized group of thieves would create a criminal city and make raids on near by points of interest while hoping to make it back with the loot before being caught. The counter is to just play somewhere else. Each island is big, travel is slow, and most of a characters assets are in very safe places. If the raider group want to move to where an established group is in order to prey on them, they are fighting an uphill battle the whole way.
It has been stated that a maurading group of players -could- raid a town and seize assets from the towns coffers if victorious. However this takes 3 days notification, a timed event, and if you do not have access to catapults then practically impossible vs a town with wood palisades.
Hopefully this helps some.