(1)
See an attached "history.get.patch"
It will fix support for countOutput, groupCount parameters.

After the fixes, generated SQLs are:
SELECT count(h.itemid) as rowscount,h.itemid FROM history_uint h WHERE (h.itemid IN ('25461','26249')) AND h.itemid BETWEEN 000000000000000 AND 099999999999999 GROUP BY h.itemid
SELECT count(h.itemid) as rowscount,i.hostid FROM history_uint h,items i WHERE (i.hostid IN ('10106','10017')) AND h.itemid=i.itemid AND i.hostid BETWEEN 000000000000000 AND 099999999999999 GROUP BY i.hostid

The patch tested of course.

(2)
Also, consider to remove from API and documentation a parameter "groupOutput". More about the "groupOutput" you can read in ZBX-5117
history.get it's a single method where this option available, it's a "not standard" parameter, it's strange for me and as I see it not used in the code anywhere.
Try and you will see that it doesn't have any affect:
"sortfield":"clock",
"groupOutput":1,
and Apache with this parameter uses CPU A LOT AND VEEEEEERY LONG TIME !!! (try for 20000 returned values)

(3)
Please explain in documentation what a "triggerids" means, does it work at all ?