It stops attacks only, abilities can still be used and Chrys/Physalias poison is an ability, not an attack.
If you suggest it should stop abilities as well, then sundials would be pretty boring - creature abilities is one of the funnier parts of the game.
Also your creatures can also use abilities while a sundial is in play, so you can eg. eat those physalias with an oty, or mutate them with a fallen druid.
And remember that weapons still work normally when a sundial is in play, but momentum does not. (sundial stops creatures from attacking, but a 'non flying' weapon is not a creature; momentum ignores shields, but sundial is not a shield)
So in my opinion it is alright as it is right now.