I agree with Anska: if I read the words Astarion and kisses one more time, I will explode.
But op, you attributing Astarions negative traits with being queer is very problematic. Astarion being such an ass in the first act comes from him being tortured for 200 years and having forgotten, how normal social interactions work. Plus the fact, that he is angry that no one helped him and now we bend over backwards to help every poor soul, if playing good. Astarion not ascending and developing his character further, is dealing with his past in an adult and healthy manner, while him ascending is taking the easy way out and getting corrupted along the way ( don't forget, that there is also the deal with Mephisto involved). Nothing more, nothing less.
The companion stories are often tied to how power corrupts - Lae'zel staying faithful to Vlaakith and becoming her honour guard will kill her, Shadowheart becoming head of the Sharran chantry will leave her in a very unhealthy state of mind, Gale taking the Crown can get him killed or he might start a war ( according to Raphael in one of the endings) and Astarion ascending makes him this cold, calculating super vampire, that becomes closer to Cazador every day. That has nothing to do with embracing something, it's basically the same reason, Gortash became Banes Chosen: out of fear to be dominated and tortured again by Cazador/ Raphael.
