well I tried Eng in the Mist and it feel disjointed and random everything. May try more next Beta to see.
I've been playing Mesmer and Guardian.
Guardian do well on PVE. PVP.. I feel the lack of Range makes him useless. It doesn't help that If I run up to be front line I drop quick.
Mesmer PVE wise is exactly what Evalissa said. Illusions does nothing while Mobs just Beeline for you. I can't take on more than 1 mob w/o dying. The same mobs I have no problem at all w/ Guardians. this including dodging, switching weapons, using different utility abilities and heals.
PVP wise. Mesmer feel like they are jsut making extra targets for enemy to kills. dmg wise, we're not doing much and we barely have any real AOE. Shatter currently isn't doing much and most Illusions died before they Run up to the target to explode... AOE and Terrain is the bane of illusions Shatter. Doesn't help that they reduce Clones dmg alot.
I posted this suggestion Official Beta.. In hopes for them to overhaul the Illusion system.
POST:
I understand that Mesmer is still being tweak being that it’s the last class that is implemented.
Current issues including: Clones summoning that override Phantasm, Shatter that doesn’t do much, the AI in ability to find target due to Terrain.
I’ve noticed that Clones was tweaked to have more health but do less damage during BWE2. Phantasm Haste is “bugged” according to alot of people.
Here’s my suggestions:
1) Shatter only Shatter CLONES. (not Phantasm)
2) Allow Maximum of 2 (or keep it 3 Clones)
3) Clones do small damage like now, but have enough health to be distraction/decoy.
4) Phantasm are summon like before but does not count toward Clones maximum.
5) Once summoned the same ability change to Shattered that Particular Phantasm with added effect. (eg. Berserker Cripple when shatter)
6) Once Phantasm Shattered that’s when the CoolDown starts, before another of the same type can be summon again.
7) Shattering Phantasm is a Projectile or a Leap (for combo reason) so Terrain problem is avoided for Phantasm Shatter. so Mage turn into a bolt, Berzerker turn into flying Illusion 2-handed sword toward target.. Etc.

Current list I have: Berserker= Cripple+dmg(aoe like other shatter), Duelist=Blind+dmg, Swordman=Bleed, Disenchanter = DMG+Remove 1 Boom, Defender=dmg+1 Aegis buff, Warlock = dmg+aoe Random conditions, Mage=dmg+Aoe Confusion…
This will allow 2(or 3) max Clones and 2 Phantasm. will Eliminated Clones overriding Phantasm.
Would it be asking too much to allow 1 phantasm summon w/o Target? (maybe as a Trait?)
Also, the Main Hand weapon for single is a bit limited. Any chance of Main handing Dagger or Pistol for Range?
That’s my suggestions..