With max clarity you can drain as much as you want for those 2 minutes and with enlightment up also.
About B.freya and Valakas, both have reuse bonus. If you get killed by your oponent because he lands some debuffs on you (like fear for example) i suggest you use b.freya.
Onslaught of Pa'agrio lvl.1
Attacks near the enemy with 4312 Power added to P. Atk., causes burns for 15 seconds, and makes him consume 92 HP every second. Requires a blunt weapon. Over-hit is possible. (when kiting you count on that not on the damage you do when actualy cast the skill.)