An hour? For gloom?!?
Joseph, the key to doing DoA successfully is having a well-suited team for it. Rit's and Necro's are great, but rangers and dervs generally don't have much use; if you want to roll through all four areas, take a look at the Platoon build on PvX. Even teams that are new to running that don't usually take more than 2 hours for all 4, and Mallyx in under 15 minutes. You don't even have to stick to that build; what I've found works well is an imbagon/ST shelter rit, 3 DwG bombers, one SoS, one AotL, and two monks running HB and UA. With the exception of maybe Mallyx (where you want to avoid enchantments and conditions/hexes) that will power through any of the areas; gloom goes in under 15 minutes.
Another thing: if you had trouble with the mobs in Gloom, you're going to have trouble in Foundry; over-aggro there (especially in the third room) and you're going to wipe. Fortunately, as long as you have a well balanced team with some decent players, it doesn't take long to learn DoA; I had it down to memory in under 2 trips. Again, I highly recommend the above stated team format, though there is certainly some wiggle room, and truly good players can handle most areas with any balanced team; the one I listed is just what I've found to be easiest/fastest. Hope this helped!