I want to continue catching water, so a narrow in depth but wide water catchment system would be useful, but also need to drain off overflow.

You should have a nice, wide landing at the base of the steps. Given their size, I would say 4' depth times the width of steps.

You'll need to add barrels (or some other larger container) and link them. Grade should slope away from the house, and from the landing, so that water runs away.

Concrete landing?

Handrails and guardrails on the deck is the first order of business.

No required for code given this height and width. We've long since had the inspection.

Urban Lavaca:

I count 5 risers, you're only allowed less than 3 to not have to have a handrail. You're telling me that those 5 risers are less than 30" high, so you don't need a guardrail either?

Code or no code, when grandma falls down the stairs or off the end of the deck you’ll wish you had railings. I think code is 30 inches off the ground where I live and four or more risers require railings. Even with out the regulations I’d want something to hold onto when coming down the stairs. And i’d Be the first one to get distracted and do a double axel off the end of the deck.

I'd also suggest trimming back the step treads to just a 1" overhang past the outermost stringers. That huge overhang you have is why the wood is already starting to twist and the end of each board is pointing a different direction. Do a handrail right at the house corner and you'll be a lot safer.

Stupid question - when you say you intended to create a downspout, does that mean you have a gutter but no downspout? So water is shooting out the gutter to land in the barrel? If I'm understanding that correctly, you need a downspout. Downspout goes into rain barrel, there's an overflow pipe at the top of the barrel, and that is piped away from the foundation. If you have that volume of water just dumping there from on high, that's a huge part of the problem

"I'd also suggest trimming back the step treads to just a 1" overhang past the outermost stringers. That huge overhang you have is why the wood is already starting to twist and the end of each board is pointing a different direction."

There is too much span between stringers and the ends of the treads are cantilevered too far.

@Joseph you mean steps shouldn't feel bouncy as you go down? WEIRD. :)

Yes, we plan a downspout. We have 4 other barrels with downspouts, just haven't set this one up. The setting is a bit different and I was trying to figure out something else that would work and be moderately attractive.
Thanks for the helpful tips!