What are the [party] mechanics behind Tera?
You can read a quick synopsis on the official site by reading the game guide entry for groups. However, to offer a complete answer, I'll address each of your points below.
Does being in a party net more experience than being solo?
If you're asking if mobs are worth more experience, then the answer is 'yes'. Being in a party nets the group 20% more experience after the original XP is split.
For a mob that is worth 100 XP:
- 1 person will get 100 XP.
- 2 people will get 70 XP apiece.
- 3 people will get 53.33 XP apiece.
- 4 people will get 45 XP apiece.
- 5 people will get 40 XP apiece.
[Does the party receive] more or less [loot] drops?
The drops are the same. However, you get better quest rewards from quests that typically require a group than you would from quests designed to be soloable.
Does the exp rate per individual change with the size of the party?
Yes. It will vary depending on both the number of people in the party and the levels of people in the party. If you are all the same level, you will all get the same amount of experience. Higher-level people will get a larger share of the experience.
Is there an optimum sized party for the optimal amount of experience?
What you really want to figure out is the experience you can gain per hour when you are solo vs. when you are in various groups with various people. Even though it's true that a mob is worth more experience if you group up, your character will get less experience than you would have if you had killed it by yourself. However, it will also die faster since it's taking damage more quickly. The idea is to see whether your play style means you earn more experience per hour faster by yourself or with others helping you.
All things being equal, you should end up leveling faster in a group.
Additional note: Quests are still worth the same amount of experience regardless of whether or not you are in a party. More people in your party usually means you can complete more quests per hour. This will boost your XP per hour substantially.
It looks like the monster has a limitied "memory" of last players' actions (size unknown). Most recent action removes the oldest one from the memory.
Some actions generate a lot of threat: taunts, massive damage, especially criticals, heals. If the player's threat accumulated from most recent actions is bigger than any other player's in the group, he gets aggro. That's why tank needs to constantly generate new threat. And that's why all you need to do to lose aggro is to run away for a while and let others generate even a little threat and push out your actions from the monster's memory. The more attacks hit monster in a meanwhile, the faster aggro will get back to the tank. This is the reason for supporters to use the regular attacks between threat-generating heals.
Best Answer
According to this guy's guide, about half way down in Gear Stats, attack speed is indeed a critical stat, as it does increase your healing animations' speed according to this line:
This guide also states that attack speed is a useful stat when it goes over all of the stats.
Finally, someone on these forums says that you heal faster with it. That topic is from 2012, and it says that there can be disadvantages to attack speed. This mostly seems to be the ranges of melee attacks. These range changes could have changed since this post.
Overall, I've seen several places say that it increases your healing speed, so at the very least, it shouldn't hurt it.