You can farm Tier 6 mats from various “heavy Bags” in different maps. In Orr you get heavy moldy bags, from 78 and up dredges heavy miners bags. Keep in mind to get the “chance” for a tier 6 mat from these bags they should come from level 78 and up mobs. However you will have to deal with the anti-farming code and diminishing returns.
Tier 5 items are easier to gather so what I end up doing for ectos is gather enough tier 5 mats, make a tier 5 item (yellow-rare) and then decon it for the chance at ectos. Using a Black Lion salvage kit on a good day I can make up to 15 ectos for an hour or two of farming. On bad days maybe 6 or 7.
The other option is world events which usually will get you one rare per day per event which can be deconned for ectos. (dragons for example) I say usually as there is currently quite a discussion elsewhere over the whole loot mechanic.