to tell you the truth, no other secondary powers other than those i have now actually impress me, they're all melee, dangerous for a blaster imho, unless you are seriously protected by FF or a super healer is close by...but you mention endurance issues, then i'd get conserve power as fast as possible, it did great things for me...i have dropped energy torrent because pre-nova it was useless to me, now with explosive blast, soon to be taken back enegy torrent, and nova, im going for a mob arrest-type of toon
https://forums.windrivers.com/images.../2006/04/1.gif phase shift will be useful, guaranteed, u never know when you'll get a surprise mob that just didnt get hit at all by all ur blasts (like those damn PPs ) phase out, wait till they lose that uber power, phase in, explode in their face, and voila!
https://forums.windrivers.com/images.../2007/09/1.gif
my pool powers are flight, SS, stealth, and fitness. im very satisfied with everything so far. ill look him up on heroplanner and post his build if u want, might help you in determining where you want to go with dynamo