According to my calculations 1 pull will, on average, result in 1.58 pulls:
1*0.68 + 2*0.2 + 3*0.06 + 4*0.026 + 5*0.012 + 6*0.009 + 7*0.006 + 8*0.004 + 9*0.002 + 10*0.001 = 1.58
Which means average chance for 5* in single pull (not considering HotM or eventual Secret Summon) is 0.025*1.58 = 0.0395 = 3.95%
So compared to Solstice or BF, that one had chance for 5* was 3.8%.
BUT this portal is more expensive so maybe Solstice or BF is still better option. Now important thing is whether Secret Summon (HotM is meh, so nobody cares anyway) is calculated just from that one summon or all bonus summons.