In general, insurance paid for by rental companies is very very expensive. It is going to be $20/day or more - that adds up a lot over 2 weeks.
If you rent cars a lot, you're better off just paying for a no-car liability policy - they're $120 or so I think for 6 months (or maybe a year?).
As for other coverages, the credit card is the way to go.
I can attest that they work as advertised. I was an ex-pat in Japan in the Y2K era. On one trip to my corporate HQ in California - I flew in arriving in the am, worked all day, then departed to drive for my parent's house on a Friday. That was a terrible mistake then. It took me 4 hours just to get past the Casa de Fruta (about 60 miles).
I fell asleep at the wheel past the mountains on the 152 highway and woke up in time to not hit the wooden fences beside the highway; turned back before going into the field but then had to steer between the fence and a concrete culvert overpass - the latter which would have been very bad.
I jump the small streambed (which was dry I think), bounced a bit off the side of the concrete culvert as evidenced by a smear of paint, and skidded to a stop on the other side of the stream bed.
Air bag goes off, but pretty much did nothing.
Car is totaled. Not smashed up but definitely a bit crinkled, but I am perfectly fine - I got out of the car and walked around for 10-15 minutes trying to get a signal before a California Highway Patrol stops to help.
I had no car insurance because I lived in Japan and had no car. This was the only car accident I've ever been a driver in since I repainted a girl's bumper as a pizza delivery driver in the 80s...
Credit car company paid in full (AA AMEX).