Think of it this way: Would Anders have been able to blow up the Chantry had Hawke not been around? Would Meredith have the Red Lyrium Sword without the expedition that Hawke funded. Hawke was there, Hawke broke the seals, whether or not the seals were weakening.
1 Hawke can decide not to let Anders get the ingredients,or he/she can kick anders out of the group.it is not necessarily Hawkes fault.
Besides,other characters presumably have free will,why do we blame Hawke for their actions?
2Bartrand not only funded the expedition,he discovered the thaig and planned the expedition long before hawke arrived.Bartrand stole the idol and trapped hawke and co in the primeval thaig.Bartrand could have done a million things with the idol but he ended up selling it to the knight commander.
It's Bartrands fault,not Hawkes.
3Hawkes family was being attacked by the carta who were being used by Janeka who wanted to free corypheus and control him.
When they went to investigate they got trapped in an ancient prison filled with darkspawn.The only way out was through Corypheus.
It's ultimately Janekas fault,if Hawke had done nothing they would have eventually killed him/her or his/her sibling and they would have opened it anyway.If they failed to obtain the blood Corypheus would have escaped eventually.