Outside of the harder to get named robes, would you still recommend robes in general for heroic leveling? As long as you can mitigate the ASF via EK enhancements and augments, I would think that the PRR/MRR from Light armor would be nice (~13% mitigation against both). You should be able to afford the -5% ASF from EK Core 2 by level 15, and as long as you avoid the chain-type light armors you should only need another 5% (e.g. EK Light Armor Proficiency, Cannith crafted, ML12 augment) to cover it.