You should check out my Abathur - Push build. I get what you are trying to do. But after a few experimentations, I got very good results over all with the build I came up with. My main issue with the long-range talent is that I often use symbiote on locust to push hard a lane (comboed with Locust Brood and nest). Also, by increasing their health on lvl 1 instead of the heal, it makes the push really strong and worth it to symbiote the locusts. You can symbiote a footman but the locust is stronger. Also, it makes a split push more effective using the monstrosity. Also at the end, you are so strong with your monstrosity (if it stayed alive long enough to kill a lot of creeps), you often end up within the top 3 of highest damage on everything if not top 1 (valla, Sgt Hammer & Azmodan are the biggest siege damage "competition").

Using my build, I find that your locust can take care of a lane without you and therefore, you can be more helpful in team fight using nest ( with the slow ) and symbiote.

Anyway, give it a try and I'm sure you will like it. Target who you want to symbiote the most in your team as soon as you start. I'm looking for Illidan, Kerrigan...any high damage melee unit in priority. Then it depends on what's going on in the game.

Oh and one last thing. With any build, as an Abathur, we are dependant on how our team perform. If they have the upper hand in the lanes most of the time, it will allow you to be agressive and to get a farther placement on the map of your hero.

Anyway, I will stop here... there is so much to say about that amazing hero...Have fun mate.

I'll leave some replay here, just for demonstration of this idea.

https://drive.google.com/file/d/0B9c2nSqv90Dld0MzZVdZWFRpWE1lV3prNElfMXhIczhqX1hr/view?usp=sharing

https://drive.google.com/file/d/0B9c2nSqv90DldTljQmltakUwbXhCSm1keVFUVEdKMVVack80/view?usp=sharing