I got my Heart from an exotic engram i bought, but your right, warlocks have been rather unlucky. Personally i'm really happy 'cause all i need is an armor that compliments voidwalker. Ever since i got the Heart, i barely played Void, except for certain bounties. It also feels like he's selling helmet engrams every week lately too. i already got 2 exotic helmets, thanks :) I didn't buy anything from Xur for 2 weeks, so this time i'm going all out. Heart is great by the way, but i do notice that everybody expects you to self rez and therefore your super is more of a 'save the strike' last resort for the team, therefore i don't know if it's the best in PVE. You tend not to use it offensively that much. It does shine in crucible though, chucking nade after nade on a zone, while their trying to capture it is great, especially with the extra after burn on it.