i guess it depends on how much attack speed she gains , but look at her skill. In terms of pure stats mehlis was already not that far ahead of the 2 other goldies. Now she loses aoe as well , on top of not gaining damage (dunno why i said range..lol). Imagine this : cyrus and barbi hit almost double per hit , in a 4x area (compared to mehlis , because she loses 50% , while the other 2 will hit in a 200% aoe).
It all depends on how fast she gets to attack and how many enemies are pressent. Having a 200% range slow cannon is pointless if there are only 2-3 , whille having a minigun with 50% aoe would be way better.