yeah .... I've run into few on Venus while roaming. Got a patrol mission where had to scout area from top of a pillar. There was one of those bad mammajammas walking round. I jumped up to small ledge till he came right next to me on other side of pillar and sneakily completed mission with him standing right below. Read online that you need Fusion rifle with Void damage to hurt them. So far I've just run and dodged them. I've been taking out the regular Vex with Pulse rifle but now wonder if Fusion would do more damage ?