Yea me and a friend got to arc 4.4 on 2 DPS builds before a marauder wiped us. I was running pretty squishy to be fair. Thinking of layering shields with Templar HoTs and pale order.

@Syiccal, like Necrotech said, none of your original ideas will work. Infinite Archive has it's own meta. You (eventually) need to build tanky with a twist. You need a solution for the marauders. You need a solution for hard-hitting DOTs. You need a solution for the little multiplying blob shards pelting you from range (not a DOT). You need to build towards and take advantage of visions.

For what it's worth, I'll share my magplar build. I've been to the latter half of arc 5 with a similar build on my own (it keeps changing from patch to patch). There may be better builds, but at least this will highlight what to look out for.

One such thing is Focused Efforts. This remains the single long-term vision that can really turn a run around for you. Some people say if you don't get 2 to 3 Focused Efforts early in a run, you may as well abandon it. I keep building for that. Other good visions include Attuned Enchantments, sustain visions, crit % visions, the scorching and the necrotic visions (for a magplar). The health regen vision can also be useful, if you build towards that, but I'm not doing so in this build:

https://www.youtube.com/watch?v=pdFsOuh1Lj4

So what's the point here? First of all note the variety and uptime of status effects covered. Once you get some Focused Efforts, these will dominate your damage output. Explosive Charge + Unleashed Terror will give you full AOE coverage of Hemorrhaging for 14s, since AFAIK the Unleashed DOT reprocs the status effect for 10s and the effect lasts for 4s each time. This is very unique. There are few ways / sets to accomplish such a thing.

Furthermore we're running dual-wield + Charged trait on the back bar, so we can have two more possible status effects from enchants. Poisoned and Burning do actual damage. Quick Cloak will auto-proc those enchants, even when we are on the front bar. In addition, I'm using Reflective Light not just for the crit, but to hit 3 targets with fire damage and potentially proc more Burning. Finally I'm using Zaan, because anything touching the Zaan beam is hit with the Burning effect guaranteed. This gives you good coverage on two of the three outright damaging status effects, Hemorrhaging and Burning.

Rest of the back bar: Honor the Dead for emergency, Channeled Focus for resistances and sustain, Explosive Charge to proc Unleashed, Meteor as the active ult.

Front bar: Sweeps and Radiant are obvious. You may start beaming from 40% in general in PvE. Dawnbreaker is mostly for the passive damage from Fighter's Guild, though I like the stun sometimes. Extended Ritual is to cleanse DOTs. Degeneration is for the Major Sorcery.

This brings us to the anti-marauder measures. My templar is a Redguard by accident, but I'm making something of the stam sustain that race brings by wearing the Esoteric Greaves. This offers some protection against one shots, cutting them in half as long as you have stamina. The other measure is weapon damage reduction. Apparently the bosses and mobs in the Archive have low weapon / spell damage. Thus reducing it is effective. The Infused trait of the main weapon is important to have 100% uptime of the enchant against a single (boss / marauder) target. Add to that Torug's Pact. This is by far the most effective measure, because the Attuned Enchantments percentage-based vision can boost this sky high into the thousands, when you start from a good base value. In addition, I scribed a Major Cowardice skill to hit the marauders with, especially when you don't get Attuned Enchantments visions.

This isn't the build to start the Archive with. The damage is not good until you get some Focused Efforts. Once you do, this starts pulling even and possibly ahead of conventional damage builds. You're also looking for some crit % visions and a little extra sustain.

One last thing to mention is that Explosive Charge is also your way to deal with the little spongy blob shards. You very much want AOE damage or an AOE interrupt (or warden shield) to deal with them. They are dangerous; sometimes they multiply like crazy. If not a marauder, then these can put an end to you in the trash fights from the middle of arc 4 onwards.

I'm now thinking of making unleashed front bar with lightning staff as those heavies are nice to rip off when can't get to close, serpents distain (heavy)on the body, and black rose prison dual wield on the back to proc the enchants etc plus it's benefits of DMG and less DMG and then pale order for the passive heals.