Quest bosses do indeed increase in difficult. That's why they are the bosses! We've seen players at ~1.5 million power defeat Baron Vega, so it can be done. Its not easy though, I'll grant you!
I agree wholly Dawnseeker!
People think Tynon is an easy game because of the auto-questing at the start.
Only until they reach the mid level heroic and quest bosses do they realize that strategy, planning, time, and endurance is required in succeeding in tynon.