The reason why the ultimate was so weak was because you were using cross laser. It had probably the strongest primary, with high damage, high piercing and firing in 4 directions. To balance this, we made the ultimate the weakest one. Anything the ultimate hits will be killed but it has a hard time hitting much. Other weapons have significantly stronger ultimates. The shotgun has an ultimate similar to Cross Laser, however instead of firing in 8 directions, it fires in 36 directions and is basically a screen clear.
Also you say it was hard not to fire and to build ultimate. It’s usually a better strategy to build up your spin in one go and then shoot for a few seconds only to continue the cycle. The only break to the cycle being firing at the chasing enemies. If you fire too much your damage becomes really low.