What exactly are the functions of the Summoner, Monk, and Samurai classes? To me, it seems that the Guardians seem to do most of the work when it comes to the tanking and quite better. Monks seem to be relegated to just moving around distracting while Samurai... I'm not so sure what they can exactly do that is of benefit. I feel that both the Assassin class and Guardian class do everything that the Samurai class can and much better. Confused about summoners as well. This is mostly about raids.
Samurai and Monks are both evasion tanks (usually), although Samurai can play a straight-up tank role like Guardians do. While Guardians are ultimately better at tanking (since they can equip shields, unlike the other two), Samurai seem to have stronger attack skills, although they also have longer cooldowns. Even Guardians’ cooldowns, though, can be pretty long, depending on the skill.
Assassins have high DPS, but they are worse at taking hits, taking average gear into account. Since they’re mostly an offensive class, they don’t really have anything to boost their defense, so their “defensive” skills are basically ways for them to run away and/or decrease Hate (notably, though, such skills either have long cooldowns or are most effective with good tanks anyways). So while their skills may be stronger than a Samurai’s, if their tanks aren’t holding Hate well enough, they’re going to get swarmed by enemies, while a Samurai can at least take the blows.
Summoners can basically fill any role that’s necessary, so most Summoners take up a certain build. Summoners are usually popular (probably amongst casual players) because they’re the most diverse. Depending on the summon, you can provide healing support, buffs, damage mitigation, attack, or a temporary tank, for example. Azalea from Silver Sword uses his summons with to scout on enemies without being in any particular danger. Roe2 is pretty obviously attack-oriented with her Necromancer build (and Moon summons).