I had the same issue with trying to cast Tamiyo against a Yasharn. If you're not able to pay life for the Phyrexian cost for any reason (Yasharn for me, being at 1 life for OP) it seems as if the game will only allow you to cast Tamiyo for 2GGU instead of also allowing 2GUU.
I had the same issue with trying to cast Tamiyo against a Yasharn. If you're not able to pay life for the Phyrexian cost for any reason (Yasharn for me, being at 1 life for OP) it seems as if the game will only allow you to cast Tamiyo for 2GGU instead of also allowing 2GUU.