Mindbender was actually buffed such that it brings a decent amount more damage ,and the mana return turns out to be about even with PW: Sol assuming 4-5 PW: sol / minute.
Perfect usage of PW: Sol will pull ahead in raw returns. However, Mindbender brings more damage.
Remember that HF and PW: Sol are much stronger than Smite because they're less costly (one is free!), and that the dot can continually trigger ToF. Actively seek out 35-40% health adds and use them as high priority HF/PW: sol targets to assist in ToF uptimes.
The only time I'd rely heavily on Smite to build up AA is during a burn phase where gosh dang it I need it now (which honestly, if you're hitting Hf/Penance on CD, you should only need a few panic-smites) or at the beginning of a fight under Hero, in which you can get AA up very quickly with hf, penance, smite smite smite.