So I watched your videos and I'll jot down a few tips based on my own experience. Do with them what you wish :-)
I greatly prefer the green reroll thing instead of the purple one. So I can reroll which boons I'm offered, rather than which gods. This in combination with picking the keepsakes of the gods you want greatly helps in forcing a desired build. Which will make your runs a lot more consistent. I tend to prioritize finding the right boons early on.
If you're struggling, I would focus on builds that use the shield or spear special so you can apply damage safely and without being locked to one place for too long. For the spear, I do Chain Skewer or Exploding Launcher. For the shield, I honestly don't think any hammer upgrade is amazing for this strategy. Dread Flight makes it take way too long to return.
For boons I pick ones with curses that have a lot of impact with just one hit. Preferably Poseidon or Zeus, since their respective curses (Rupture and Jolted) are very strong and add a lot of damage. Their duo boon is also strong. If you go with Zeus and Ares, their duo is great to just stack revenge boons. Adds a lot of passive damage to enemies. I greatly prefer Athena's dash to all the others, since it's one of the easiest ways to reflect projectiles IMO (the other being Athena's sword special but that's another story). This saves a lot of damage for the times you dodge in the wrong direction/timing is off.
One of the most important things for many builds is to have access to two easily applicable curses/status effects. This activates Privileged Status which is a massive boost to your damage. Look for curses that last for a long time. Demeter's does, Jolted and Rupture do, Aphrodite's can get increased duration.
Finally, I get the feeling from watching your fight against Theseus and Asterius that either you don't know their patterns very well, or you're a bit impatient. For Asterius, keep away when he swings, then dash straight at him when he jumps so he flies past you. He'll follow up swings with his jumps 0-3 times. Give him a couple of whacks then get the hell out of there because he sometimes swings without windup. When he does the bull rush, dodge through a pillar to make him crash into it. Rinse and repeat. Keep a pillar between you and Theseus every time he wants to throw his spear (or deflect it). Once it's only Theseus left, be patient. Keep your distance and let him throw his spear. He always shows his back after, which lets you get a bunch of free hits. This way, you can focus on dodging the god's wrath and just whittle away. With a proper boon build you'll still melt them quickly. As you get more comfortable you can start being more in their face.
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Stop being so aggressively argumentative for no reason. - UnfairRepresent