Let me try my best to explain why each of those builds do wonder agaisnt thieves in general. I don’t really care if I’m overdoing it, but I like to give the full thing (from me, as best as possible) as much as I can!
DISCLAIMER: Much of my arguement is still speculative and is subjected to correction. In other words, I don’t know much about mesmer vs thief gameplay.
Know that the core mechanic for thieves is to quickly take down enemies and then find some other poor lost soul for them to take out, Assassin’s Creed style. Essentially it’s why thieves have lots of good stealth, powerful bursts, and unique ways to dodge potentially fatal attacks from enemies. While this makes them formidable foes, they can’t stay in a prolonged fight. They are innately squishy and if the fight drags on (assuming no outside interruptions), the thief becomes vulnerable each moment.
From what I understood from my matches, thieves trump over Power Shatter mesmers because they can simply evade the frequent 10 second spike bursts. Not only that, but in this partcular fight, mesmers don’t have a lot of defense agaisnt a thief and this sentence is just the blurb of it. Thieves can infamously reset fights if they want to with their stealth and then come back to restart and win this time. A Power Shatter mesmer’s defense (shatter invulerability and 2 stealth skills) don’t amount enough for us to take them on at equal footing.
These builds help out to beat up thieves 1v1:
Prismatic Understanding Condition – Mesmers have stealth too! Only this time we get 60% chance of defensive boons and a buttload of stealth! In this build, a mesmer’s 3-4 stealth (max if taking Torch 4, Decoy, Veil (it’s the line stealth), and Mass Invisibility) is a significant amount to a thief’s 2 stealth skills. Even though one’s a healing/prolonged stealth utility skill for a thief, a mesmer can simply pop in and out of stealth while being defensive and inflicting conditions. And conditions are sustained damage attacks which the thieves can’t handle neatly. I’ll get to the sustained damage part later. The stealth isn’t the only defensive part for the PU Condi. Staff skills give Chaos Armor and the Scepter skills give defensive blocks. With these, you give no leeway for thieves to use their coup de grace.
Shatter Condition – Now with Maim the Disillusioned, we’ve become the masters of Torment. Thieves pride themselves in moving around the battlefield like a maniac. If we give them a condition that doubles the damage because they move, then their core mechanic is under threat. Unlike power shatter, where they rely on a single powerful burst, shatter effects are consistenly sustaining damage. Plus unlike power shatter, we gain block skills and an extra stealth skill to guard ourselves against them, assuming Scepter and Torch. The Staff skills help because they give out conditions and a good niche of Chaos Armor. It’s a more offensive version unlike the PU build, but an equally potent one.
Lockdown – If a thief can’t do anything, it’s a sucky thief. And this is what our lockdown has an advantage against thieves in general. We have 5 lockdown skills: 2 from our weapon sets, 2 from our mantra, and 1 from our shatter. That’s more than enough for us to interrupt the thief and make them truly vulnerable. Our best defense against bursty thief, in this particular build, is also a full on offense. If one traits Chaotic Interruption, we not only root them but give out another condtion where they can’t maneuver much. With these, they become sitting ducks if they’re not careful. What not better way to do than to make sure that their skill sets useless like fish?
Power Phantasm – The classic phantasm and the reason I love using this build against thieves. This is the reciprocal to the Power Shatter, but our ‘burst’ damage comes from our phantasms. The key tactic to a phantasm user is to let our phantasms do the work and we just fend for themselves. A ‘Pure Phantasm’ build, which has Sword+Sword/Scepter+Pistol, has the two most powerful phantasms in the mesmer kitten nal, 2 blocks from each weapon set, and other fun utilities that we can use to counterattack. A ‘Offensive Version’ helps as the phantasms do damage and we can dodge roll/stealth whatever we want. If the thief attempts to restart the fight, the phantasms will be there waiting.
If I didn’t explain well, I understand. Much of it’s a summarized blurb of why these things are good against thieves.
