Patch made this stronger.

Artifact Mystical seal of Protection - restart until 2 powers (ideally 2 lvl 2 powers) in first room
Daybreak + Light Attacks or Light Embrace or Revival
Aim to get Torrential strike every time.
Dillution + Torrential Strike or Water Attacks or Pressure Nozzle or When it Rains.
Mastery -75% proj/effect damage, asap.
Perfect every room for +6 inspiration, until first miniboss.
Chairman - Artifact Manhole cover
With Daybreak and Dillution, either artifact will help get Bright Spring
If you can get portal of scarcity after Bright Spring (after the street fight miniboss following Karai), you're probably in a really good position.
Precision is very good. Mastery 10% multihit is good. Mastery Multihit Damage is good. In that order, but depending on your damage mods
Hardened Shell is best in tool slot.
Bright spring does not seem to be affected by Plundered Pizza or turtle passives. Hits on shields count. Hitting 2 opponents once is only a heal for 2. If you multihit OR crit, it's 4. If you multi AND crit it's 8. Targeting individuals can gain you more health than aoe.

Michelangelo's Insight + max dragon upgrade is +45% chance by default, to multihit. It goes up to 80% with lvl2 Torrential Strike and 90% with multihit mastery. When it Rains damage, plus Bright Spring health, plus crits, plus stacking Daybreak, plus Light Embrace, you end up with respectable damage and the best survivability. Later, you face-tank most everything.

Tips:
You want around 500hp. This is important for Light Attacks (health based damage) and surviving tough fights with too much damage.
You still need dash/dodge and hardened shell to keep from tanking big hits early on.
If you have bright spring, don't be afraid to farm auto-spawns in miniboss fights (street fights) to heal up.
Illumination and Eternal Light (if you have Shimmering Shield) are probably the weakest light powers you want to get.
The miniboss before the roof chairman is the last room before shredder. Might as well take a room boost.
Grab the Artifact Astral Charm or Artifact Turnstone or Artifact War Staff, depending on your confidence.
Hardened shell + 120% special cd reduction + dragon coin passives makes you basically invulnerable, as long as you have something to hit.