In Formal letters^x, Phrasal verbs^x

I would use "regarding" or "in regard to" instead of "as regards." I'd like to hear from British English users as well as Americans from other regions to hear their opinion of "as regards." It sounds wrong to me, but it's probably just a regional thing. You can use idiomatic language in...

A s regards computer games, I am very exacting. I am very exacting a s regards computer games. What about those? Also I would like to know if the next statements are true. "As regards" is an idiom. I don't believe it but I found this - http://idioms.thefreedictionary.com/as+regards You can't...

Why we can't use phrasal verbs in formal letters? Could someone explain it? Where can I read about it? What about sentences such as: We hope to HEAR FROM you soon. Thank you in advance. Best Regards Martin