Diablo – Does the 2-piece Marauder’s bonus also affect the Companion active ability

Companion damage scales based on attack speed. This was confirmed by Bashiok and tested by theorycrafters, who arrived at these numbers*:

APS    Companion Damage
1.00   30%
1.34   40%
1.40   42%
1.43   43%
1.60   48%
1.84   55%

*Calculated by looking at the in-game tool-tip, which changes based on the APS of the character.
Note: The wolf, being a shorter duration (25 seconds), does twice the %.

That is, the companion does the % of your weapon damage based on your APS. If it follows this logic of being a channeled DoT (which is what most theorycrafters have come to agree), then based on Bashiok's post, the tick rate (how often it attacks) increases as your APS increases. As for speed it attacks, it would behave like any other DoT in this situation. It would attack once per cycle for its inherent percentage, so if your APS is 1, it attacks once per second for 30% weapon damage. If your APS is 1.6, your cycle time decreases to 0.625 seconds per attack (1/1.6), so it would attack once every 0.625 seconds for 48% weapon damage. If it follows this model, your weapon damage would have nothing to do with companion damage, but its speed (and therefore indirectly, its dps) would affect companion damage.

As for the boar companion, it says on the wiki that it "strikes multiple enemies with every swing."

Edit: After some testing with a level 60 demon hunter, it appears that the percentages are roughly correct. For the ferrets, even though they are animated to attack separately, it seems the total damage is split between the two. The boar is really hard to judge, but as far as I can tell, the damage is the same as the others, just as a cleave attack that hits enemies in front of the boar for full damage to each.

All this information is gathered by personal experience or by experiences posted on Diablo forums that were confirmed by more than one person. It's difficult to get exact answers until everyone starts posting their findings, since Blizzard rarely explains how game mechanics work.

I do not personally have the set, but based on conversations in this thread, I will say the following regarding Asheara's Vestments:

• When followers are summoned, they will have the gear and skills you actually equip them with (so the dps and tankyness are dependent upon how you gear them)
• The followers are up very often if not practically all the time.
• The followers are often all three out, though they do occasionally come in one at a time.
• The followers can be summoned even in multiplayer games.

Relevant quotes:

The damage they add is however much they have when equipped. They are your actual followers and their equip. I ran with a witch Doctor who had them out almost permanently.

Brock - yes, I was playing last night in adventure mode doing Rifts on public games. All 3 followers come out; however sometimes it seems they come out one at a time.

If you are playing a private game, and already have a follower in your party, only the other 2 followers will appear. But don't forget to equip your followers with good gear; I would advise that the followers at least do something in the ~100k damage range.

Just to add, I crafted 3 and got a ring of royal grandeur, so I now have the 4 piece set bonus. I timed it and did multiple experiments.

The duration of summoned followers is 30 seconds. The proc rate was significantly higher on AOE packs, almost guaranteed within the first couple of multishot casts, where it was somewhat lower on small packs and elite packs, but they still came out pretty reliably even after a few hits. I'd say you have a good chance of these guys being out 2/3 to 3/4 of the time, so it's a good set to get, especially if you can get your followers some good weapons, and get them the tokens that unlock all abilities