No.

We are given the task to investigate that abandoned prison where some weird experiments were conducted on the prisoners. We've explored it more than once so we're not expecting to find anything special besides the usual signs of atrocities committed there. But what is that? The monsters in this mission are much stronger than normal. And who is that girl in chains? She looks like... no, no, no, that cannot be possible! We must save her at any cost!

What kind of jobs or skills can the main character (PC) have?

From the start you can create 5 types of characters for your team: fighter, "shooter", "healer/support", wizard (buffer/debuffer) and warlock (elemental damage dealer). As you do quests, others will pledge allegiance to your family and you can create them as well and they are really different. Cannon shooters, summoners, masters of martial arts, minstrels - you name it. Most of them have a story of their own that is sometimes a reference to something (a certain ex-pirate captain's quest reminds me of Tarantino's "Kill Bill" for example).

Wow, this sounds really fun! Is the game a typical WOW hack n slash combat?

Not quite. You control a team of up to three family (yeah, that's what you play as, a whole family of nobles; those who join you become part of the family as well. BTW, on startup you choose the family name and when you create new characters, you pick their first names only) members and you can control them all at once, choose two of the three or any single one of them. Their currently active skills are all assigned to hotkeys so you don't need to switch to the character that you want to use a skill. The thing that really simplifies most of the "kill X mobs Y" quests is the Keep Mode: when it's active, characters attack the nearest enemy and healers heal the nearest wounded ally. If the enemies are of flying type, you can't hit them in melee with a normal attack (certain skills can still damage them though) so that's where "shooters" and mages come in handy (wizards and some of the recruited characters can fly at the expense of mana points, making them nearly invulnerable to ground melee monsters).
Other than that yeah, it's "click and they'll attack".

Is it a fairly new MMO? Is it isometric?

Not quite new, next year it's going to celebrate 10 year anniversary. And it's not isometric (although the camera is always centered on the active character, you can change the angle of view and how close to the character the camera is easily).

Huh. Can you describe something famous, recognizable from the MMO?

You mean besides the fact that it's a Multi-Character Control MMO about exploration of the New World with fantasy elements? I'll try.

One of the recruitable characters is a mechanical doll that is, however, self-aware and has feelings of her own. Getting her is somewhat annoying as you'll have to gather her piece by piece, farming for her hands, arms, legs, feet, heart, chest and pelvis on two levels of a mansion. Here's her story:
The mansion belongs to a certain Doctor of Alchemy who created weapons of immense power for the queen, but after one of his inventions was used to wipe out a whole fleet, he was terrified at what he has done and fled to the New World. He had a daughter, Catherine, who died of a virulent disease when she was young (well, not really, but we get to know the truth much later). The alchemist tried to resurrect her but failed. Then he encloistered himself in his mansion and tried to create a mechanical copy of Catherine, perfecting the technology of building mechanical dolls powered by a certain magical substance (the results of his tests still haunt the mansion and attack intruders). That's where you come in: you help the grieving father prepare everything for the final phase, gather all the components and witness Catherine's "rebirth". He then entrusts the doll to you so that she got to see the world and learn new things.

One of the peculiar traits of the game is the mechanic of so-called "stances".
Basically a stance is a combination of up to five skills that levels independently from the character (stance experience is earned when monsters are killed while a character is using the stance, no matter who of the team/allies kills them). Each stance is maxed at level 25 and usually receives progressive bonuses to secondary stats (e.g. Attack Speed, Block rate, Accuracy or others) at higher levels. Each time a stance is leveled up, a certain quantity of stance skill points is earned, which can be spent on upgrading skills of that stance up to level 10 (skills can have higher levels, but those are only achieved through equipment or buffs).
Also, a stance determines what "weapons" (well, some of the equipment of "weapon" type is not meant for direct attacks, e.g. rosarios, construction hammers, pendants) a character may use, although different characters can have different variants of the same stance (an ex-pirate captain uses saber and pistol in her variant of a certain stance while a normal fighter uses sword and pistol in his/hers). Stances can be switched at any moment in combat, provided a "weapon" corresponding to them is equipped.

Granado Espada.

You are correct. :-)

I might add that it's the only MMO that keeps me interested in it for more than a couple of years already, others lasted from half an hour (WoW) to half a year (SW: tOR, Lineage 2).

I'll go with the game I'm currently playing.

It features an orphan, a princess, an old man, and a pirate.

Final Fantasy XII?

Not what I was thinking, but close.