[2020] PSA for new players: GW2 has an Action Camera Mode.

When using action camera, you can use the "snap ground target to current target" option in order to alleviate this problem. You can check the checkbox under the Combat/Movement general options section, or if you don't want snap ground targeting on all the time there are keybinds you can use to toggle it as needed under the Targeting keybinds section. When target snap is active, if you aim the camera more than 90% downward, the ground targeting marker will be placed at your feet rather than under the crosshair, even if you have a target selected. There are some skills which will ignore target snap (such as shadowsteps), but by and large this should work. Hopefully this helps!

This has been on my "annoyances I sure would like to fix some day" list for a while now. I've made a few attempts at a fix in my spare time, but inevitably the side effects end up being worse and other stuff ends up taking priority over continued investigation. The harsh reality of development is that there's always way more stuff that needs doing than time to do it in, so here we are.

This may not be precisely what you want, but maybe it will be close enough. While in action camera mode, if you have skill 1 flagged to autocast (ctrl+right click) and you press 1 rather than left mouse, you will autocast skill 1 on your current target until you drop the target or leave skill range (more or less what autocast on a skill would normally do).