Found a solution for the delay, please try it and report if it helps you and even more important if it doesn't break something else.
Special testing should be done for HD channels with high streams.

Change line 77 in xine_input_vdr.c
from:
#define METRONOM_PREBUFFER_VAL (4 * 90000 / 25 )

to:
#define METRONOM_PREBUFFER_VAL 128//(4 * 90000 / 25 )

so from 14400 to 128 lol, making it smaller helps with higher streams?

Some documentation says something that large buffers are needed for "mosaic" channels (what is it anyway?).
Looks like there is another buffer somewhere on the way...

Please report the results.

Thanks.