Odium is hatred, which is not necessarily killing. If anything, Ruin would be the supreme killing force, and the only reason Preservation could hold up under his assault was because he was self-preserving. We just don't know enough to brush off Odium's power as part of his intent.
As Sazed points out, minutes pass like hours to a shard. So by brief, Hoid either means in human time, which is not very long, or in Shardic time, which is even shorter.