while being as tanky as a brick for their immense speed (the Doom has 1250 armor
They have more armor than most other ships in their hull size but their total hull isn't anything special. Doom only has 7000 hull, that's less than other cruisers except falcon and fury which are both fast cruisers, and heron but that's a carrier and the rest are not intended for combat. A far cry from an actual brick like dominator with 14k hull and more armor or venture that has the same armor and 3k more hull. Once you get through their armor, they get too scared to come out of phase, flux out, and die. Which is the key to beating them.
Vs Phase really comes down to winning the staring contest and forcing that contest in the first place. To that end, keeping your ships close together so phase ships can't find open flanks and having good anti armor to force them to cloak or take damage. HIL, hephaestus, tachyon, phase lance, maulers, etc. Certain bombers work well too, pirahnas (a bunch of condors can beat zigg with pirahnas handly) and flash create big fields the phase ships can't afford to uncloak in without getting demolished, missile/torp bombers are less useful because of timing issues. Warthogs can be a menace and xyphos or thunders mean any ship that unphases is immediately locked down. Just watch out for dooms planting mines on top of fighters right next to ships for cheap hits. In the worst case scenario, you can force them to phase as much as possible until CR death. Phase cloak has a 3x time dilation, meaning for every 1 second of ppt you spend, they spend 3 and high tech phase ships also have delicate machinery so once their ppt is up, they lose CR fast.
"instant" high alpha damage weapons such as needlers, sabots, burst PD, IR autolance, and phase lances do well vs phase enemies. Alpha striking a phase ship when it just emerges from phase to attack, before it can rephase, is key to fighting them close.
Alpha weapons are good but needlers and sabots are not really the best examples of weapons to use against phase ships. Needlers due basically nothing to them due to low hit strength unless it's a frigate I guess. Sabots are better off because of emp and higher hit strength but I wouldn't pick sabots as my missile of choice against phase.