The Tanker's one weakness is a tendency to run low on Endurance. Since you don't take a lot of damage, there is a temptation to rush headlong into the next combat. The Tanker can't keep up this kind of pace, and if you attack without thinking, while at low Endurance, you can drop your toggle defenses, leaving yourself helpless. You should be patient, and bide your time between battles. Endurance recovers much faster than health.