In a sense, the symbiont totally eliminates the host's personality, just by merging with it. This is clearly shown in Invasive Procedures.
Once you get joined, you are no longer you. You are you AND 'it'.
I never saw any evidence of Dax the symbiont fighting against Curzon's hard drinkin', womanizing lifestyle even though 6 lifetimes should have given it the wisdom to know that's a bad idea that has pretty potentially serious consequences to it's humanoid host. It's shown in canon that Curzon died having sex in Let He Who Is Without Sin...
Great way to go, but it killed him.
Joran still kills people, with Dax gleefully watching the events because the experience will add to it's experience as a symbiont, when Dax totally could have made an effort to stop him.
It compels Jadzia to complete her, excuse me, Curzon's
(he's dead! A long time ago!) Blood Oath
with Kor, Kang and Koloth, although it's gotta know that her body has little chance of surviving, although it probably will.
It uses Ezri's memories of Jadzia's marriage to Worf give her the idea that it would be a good idea to go to the Gamma Quadrant to save his ass from the Dominion, although it could likely end up in the death of the host.
Dax has been saved from death 8 times while it's humanoid host has died, The only concern Dax has for humanoid life is when it means it's own survival.