I've written some thoughts over at the PuzzleandDragonsforum so I thought I will do a post about them here.
Dark Constellation 2.0, Hamal is a good sub for dark teams focused on dark OE and is like a mini-Eschamali for Yomi Dragon and Eschamali teams, okay as a leader but you'll probably lead with MP dragons or awoken tier cards or even Eschamali if you have her. The same goes for the light Constellation 2.0 probably and that is a good sub for Sakuya and her variations.
RGB Constellation 2.0 are better used as leaders (36x is not too bad while not even factoring in God Killer awakening which is an additional 3x for themselves and they have elemental resists for 2 colors although none of them block dark) or subs for their own team at the moment IMO because their AS produces jammers. If you use them as subs for non-jammer-based leader, you can combo their active with Constellation 1.0 or some other card that can convert jammers but I think it is situational to have to use 2 skills to do that and their actives alone is not that useful. Red and Blue can use their respective Marionettes perfectly and resist the changed color, Green can't but can use red marionette to get resistance to the changed green color without elemental advantage.
I got the red Constellation 2.0, Denebola and I think she might be a situational sub for the latest Co-Op Descended Gainaut: http://www.puzzledragonx.com/en/monster.asp?n=1839. Gainaut can also be used as her sub too.
Regarding the new GFE, Fenrir, I think it is powerful with the 10x multiplier and God Killer awakening, the highest multiplier for a card with God Type awakening at the moment; double Fenrir leads will have each Fenrir leader dealing 300x to God types! It should be able to handle a lot of high end contents. (not sure about arena 2.0 or possibly arena 1.0 though)
