Heracles still has a spot I think. Roughly same stats, so you're trading a 4 turn god slime for a slow orb change + some heals + 2 skill boost, so I suppose which is better would depend on whether you can take hits from the dungeon in question. He'd be the go to guy instead of Tengu though - only 1 less skillboost in exchange for a bunch of extra perks.
I would take echidna anyways. Those 3 turns are worth too much. Mastering for bosses with preempt status shield, golems for those dungeons with annoying 99% gravity. Good to have lots of options.
You need orb enhance for full board to be worth it, so you'd need either unicorn or a possible ult regulus/heraS in the future. And Sandy is the new shynee- try to get your hands on one.
Congratulations though - very good roll!