I would say it's fairly typical assessment.
Most folk can handle 110 to 120% of their concentric max for a prolonged negative without failure.
To me, the more pertinent question is "where do you fail on the concentric phase?" Shin, Mid, or lower thigh?
I ask that because, if you want to improve your deadlift performance, I would advocate the use of rack pulls from the point of failure up with near maximal weights after your regular pulling sessions to overlload your system. This would "groove" your body to pull maximal weights from your failure point and, arguably, improve your performance in the lift.
That said, rack pulls are something I would only recommend once or twice a month (assuming you have weekly pulling sessions). Reason being is maximal effort pulls from any range fry the CNS pretty hard. Body can't take it too often.
All the best,
Lifting heavy stuff is fun and relative......