[Avodah] Chazzan pacing the tzibur/long tachanun

[M Cohen]

I have had the same kasha.

My conclusion was that since the leniences of tachanun are very much
affected by minhag (for instance: days&situations not to say/not saying
after shkiah/short version when need to leave shul early/etc), the minhag is
includes saying it faster than the rest of dovening (and indeed this is the
common minhag both in shuls and yeshivos)

I could suggest possible reasons for this minhag, but I will leave this to
greater TCs than I.

Personally, I rarely finish all of long tachanun, but jump to shomer yisroel
when the shatz indicates that he's finishing.

mordechai cohen