For us, review latency was obviously a problem so we eliminated it (for most tickets, anyway) by making the handover synchronous. Get on a call with the reviewer when it goes into the review column. The win from eliminating review latency massively outweighs the context switch cost for the reviewer. All the more so when the patch is small enough to actually read through on the call, so if there is anything immediate to address you can ping-pong it without anything waiting.