I took a Journeyman t5 damage merc to the Arena to see how these new mercenaries work. There I matched him up a level 90 NPC sparring partner attacking from behind. I boosted the NPC's mitigatin with 30 "/increase mitigation" commands. I choose 30 because it seems to correspond to group mobs lately. In the past I used 25 but they seem to have become tougher in the newer zones. A default Test dummy has very bad mitigation giving distorted results.
I did relatively short parses using different sets of bufs. My first few tests were messed up because the mercenary seems to keep important things like disciplines from burn mode when up against a Test NPC. I got all funny results including 7k+ DPS with every single pierce attack hitting for 2976. Guessing what was going on I left the merc on balanced, zoned out, camped, reset everything and tested with an up ramp of buffs starting from nothing. Each new test includes all the bufs from previous runs. The tests are relately short, at least 15 minutes. Keeping aggro from the merc as a ranger had me using Devastating Blades, aggro poison and casting a great many Summer's Mist spells.
Bare - Merc with no bufs he doesn't cast himself.
Ranger - Strength of the Tracker Rk. III and and Yowl of the Predator Rk. III
Chanter - Speed of Ellowind Rk. II, level 72 chanter haste
Shaman - Unity of the Spirits Rk. II
Bard - Aria of the Poet Rk. II, Warmarch of Brekt Rk. II, Arcane Arietta Rk. II, Symphony of Battle click effect
Note that all of these are long term effects that one might keep running through an extended battle or grind session. There are no short clicks like epics, disciplines or AAs included. The shaman bufs do not include Champion or Lynx.
Bare - DPS 1093, Pierce 876, Stab 174, Direct 43.6, Avg Pierce 722
Ranger - DPS 1551, Pierce 1241, Stab 267, Direct 42.6, Avg Pierce 1010
Chanter - DPS 2334, Pierce 1868, Stab 425, Direct 41.2, Avg Pierce 1024
Shaman - DPS 2563, Pierce 2029, Stab 492, Direct 41.7, Avg Pierce 1134
Bard - DPS 3522, Pierce 2695, Stab 740, Direct 87, Avg Pierce 1308
Players are nothing like this. The bare mercenary hits mostly for minimum damage. Fully buffed he hits predeominantly for maximum damage. The distribution is 20 different values just like mobs and pets.
Pets are like this too. They have low attacks compared to players and respond strongly to bufs. Raising the mercenary's attack does wonders for its power. Most pets just aren't this strong. By contrast the effects of raising a player's attack can only be discerned with careful parsing.
I think it would be better if the DPS mercenaries did not get to be so powerful.