I once overloaded my 2008 Tundra with a bucket load of sand we needed for the foundation of an antenna tower we were getting ready to pour. It was probably a similar amount of weight or maybe a little more than your load of mulch. It was a probably a lot more scary driving the Tundra. Steering was super light because of the front end rising up so much, but I was careful and took it easy and made it to the destination with no problems at all.
I think there is generally a lot of margin in the safe limits if you are careful with how far you go and how fast you drive. Of course I would not recommend overloading any vehicle, but it is nice to know that you can if you have to.
I feel like the Ridgeline is every bit as capable as my old Tundra except in towing heavy loads. It's hard to beat a big engine and a heavy steel frame for towing. In many other aspects the Ridgeline is much better. If the current Ridgeline was around when I bought my Tundra I would have taken it instead. I didn't need my truck for towing really, mostly just hauling things around in the bed. The towing is just a nice bonus that I used a handful of times.
If the Ridgeline lasts as well as my Tundra did, then I will be very happy with its purchase, but I think Toyota is probably well ahead of Honda in that regard. Time will tell.
