I kind of think the exact opposite - I find the Piranha really effective on the GI because it's so good at switching from mook to mook, mowing down several of them before they are even done being staggered by your Proxy Mine. And if you use APIV on the Hurricane, it might actually be better at taking down bosses than the Piranha, due to the clip size upgrade. I haven't done the calculations though. I guess I have never really been "in love" with the GI-Hurricane. I don't know why - it's an awesome gun on a powerful character that fixes its accuracy issues, and I have seen people absolutely wreck with it. Just not my thing. I'm not great at controlling recoil, that might be the issue.
And yes, on an open map, GI-Javelin > all. And the Claymore might be better on a more open map too, seeing as how it can pretty much OSK anything at any range on the GI.
This is the build:
http://kalence.drupa...23H54384!5BFACS
The GI makes great use of the Barrage gear with this set up, you will be surprised at how much this improves the recoil. Also, the extra ammo is handy as you chew thru bullets at ungodly speed. Warp ammo for the extra damage boost, it's all about outright damage on the GI.
You can use disruptor / incendiary ammo and generate combo detonations, although IMO this slows down the GI damage output (does extra stagger to enemies however). Considering the extra damage inflicted by the Warp ammo on all but one protection, it is a great choice. Even Prime & Atlas shields are not concerning vs this set up, this GI still chews thru them.
If you are able to switch targets easily with a GI/Piranha, this build is even easier for that (having played both many many times). The GI / Piranha is slightly better vs boss armor however (maybe the best in the game short of a Talon Merc and close range)