I may be alone in this, but I wear a windproof rather than a rainproof - and a running windproof at that. My 'reasoning' is that:
1. mostly it doesn't rain
2. a running windproof is warm enough over bare arms, but not sweaty-warm, just always comfortable
3. if it rains, I put on a thin rainproof on top.
Consequently I've never felt a need for arm warmers.