The problems with the 30/12 build is that I don't think you get enough wpf to use the 10 power throw.
I'm using an old character builder but certainly it is VERY close to the border line.
Also the problem with the 30/12 build is your athletics is so low, as a thrower really speed is your old defence (unless you are a scummy thrower with a shield). High athletics not only lets you kite but it also means you can get to and pick up ammo faster.
For a thrower going foot only I don't think I'd go past 27/15, and even then I feel athletics 5 is risky.
24/18 Power Throw 8, Athletics 6, Weapon Master 3 is fairly good though very tight on skill points.
21/18 PT 7, Ath 6, WM 6, Power Strike 4 is more flexible, you put 140 ish wpf into throwing and then anything else into a backup melee.