if neptune is hyper sensitivity, they might.
i don't think people suicide because they failed to create their own unicorn ranch.
they mostly do it because they feel worthless, inferior etc.
the more blunt, the more thick skinned of a person you are, which are the anti-moon/neptune stuff, you won't give a dang. therefore you won't suicide.
the more sensitive you are chances are higher that you will fall in such a big depression, you will go and take your life in your darkest hour.
not sure about venus. for a good suicider, who will actually go and do it: i'd pair him with pluto or mars for self destroy capabilities.
maybe venus would "think" a lot about it. writes poems about it. but has no guts to do it.
I have lots of moon, neptune and I'm a libra accendent. The moon eliminates some of my saturnian traits that comes with being a capricorn. I daydream too much, I'm a complete idealist, and I'm not going to lie, my problems are merely "first world," and I do have blessings but I'm still not happy. I fantasize about death all the time and I am always in search of some spiritual awakening or a 'perfect' religion to seek some sort of salvation.
I see pluto and mars as being able to take the heat. They seem very primal. Pluto is soulfull(as you mentioned) but he certainly isn't fragile. Pluto doesn't care about reaching an ideal, he can play dirty, live in the worst conditions and he'll fall in love with it. He's aware, and he's able to transform his bad conditions to good ones with much force but he'll be fine with nothing but bread on the table. Mars is similar.
Neptune will be ungreatful in a subtle, tragic way that would sound more tragic than pathetic. Moon can sound pathetic though. Neptune is more existential depression, with venus, it's idealism unattained, expectations not reached(because libras are an idealist) etc.
Anyways, what do you think?