It's not arbitrary and frankly I've never used a RoD because it's not as good as ASR and that's all that matters.

The widely accepted "cut off" number for death costs is around 1.5M-1.8M hence my statement of "1.8M+" You can do your own personal research (since I'm assuming you're not into high level PvM otherwise you'd agree with me) but that is the accepted amount.

Players bring a RoD switch when their death cost is too high, they don't prod the ring because the increase in DPS from the ASR is good enough to merit that type of play style.

I believe I covered the only possible reason you'd want to lose out on DPS and use the RoD which is when you're learning a boss. Once you've learnt a boss, when are you gunna die? When you D/C and maybe if you do something really stupid that you know you shouldn't have done.

Also, just to touch on this; anyone who is using RoD to save themselves money - it would take them 20 -25 deaths with RoD to save themselves the cost of the RoD itself. When are you realistically going to die 25 times? I think the last time I died PvMing was 2 years ago because I misclicked res on low hp and telos 1 hit me.