5% harpy summon rate is a joke

So I tried to do I Stonesong Eyrie delve and the respawn of harpy is just plain ridulous. (Refer to xp earned)
No way!!! Is it a 5% chance or 20% with 4 harpys. It was respawning as soon as it was killed. 85 mins later I won. What a joke .Somebody needs math lessons is all I can say . I didnt even bother with 2nd fight. 20200204_222943|666x500

For the AI assume its 100% - stated chance. It better explains things … 5% for player, 95% for AI