150 is rather good for a DPSing tank.

180 sustained sounds unlikely unless the DPS tank has a full DPS setup -- 30 str, HQ crafted DPS gear, etc. Possibly MRD class not WAR job.

MRD/WARs have oddball parses because they have pretty extreme cooldowns, but peter off when the cooldowns are down. If the parse ends right after they use cooldowns, it can spike up pretty hard even in mid-length fights.

Edit:

Normal "tanking tank" DPS is in the 65-90 range depending on the situation. I've parsed DRGs in the 70-80 range. But if you're doing progression Titan (e.g. you have pre-Titan gear) and you're pulling 140, that's better than most of the playerbase.