T6 Blights on a T5 Island? That doesn't seem right...
On the satyr islands (at least on corvus) there are energyzed kwellen running arround, which are T5 mobs. There are guarded by a bunch of elite blights. Elite blights are "energy blights", if you go for the naming from T3/T4 blights, but are T6 and normaly found in the ED. The only T5 blights I know of are the Veteran Temptes Blights, and I'd suspect them to guard a T5 kwellen and not some T6 blights.
Of course it's not very convinient for a player to find T6 mobs running arround in a T5 arrea. That should be changed (someday).