I played a lot more of Hades yesterday vs. the first day, around 9 hours. Some thoughts from that.
The Tartaros boss got way easier by hour 12 compared with hour 3. Part of that could be me getting better. I've also been spending nectar to get keepsakes, dumping keys into locks, spending droplets on the mirror, and unlocking weapon changes with Titan's Blood, which adds up to a lot of progression.
The Asphodel boss also got easier from the time I first reached it (hour 6? 9?) and I think that is easier to chalk up to skill-up. The Lernaean Bone Hydra boss alternates between two attacks easy to track. When its health reaches 2/3 it summons three random-color heads. At 1/3 it summons six (?) random-color heads. The purple ones spit fireballs that persist on the ground. The green ones spit skeletons. The yellow ones I think do the ground-slam shockwave attack like the main head does. The main head attacks faster at each health milestone, it spits more homing energy darts at a time and the darts travel faster. It is easy to hide from most of these behind any of the four pillars. The darts travel slower when the extra heads are out. It helps a lot to kill one of the heads on the top left or top right side—this creates a mostly-safe foothold to kill the rest.
The railgun is pretty good. I stumbled into a build where I used it to inflict Doom on enemies to deal a lot of damage a little while in the future. (Something like Impending Doom lv2 and the attack-triggers-doom boon lv3.) I reached the end of Elysium for the first time with that build. Fun to shoot things and run away waiting for damage to hit—nice lazy way to kill enemies. I died to Theseus and Asterius.
I'm starting to remember to watch the god gauge a little bit.