Alexander would be a waste on a single SPH. Smerch would need a guided rd already loaded, not a non consequential task. ..would use those for other tasks. Coalition, especially the double barrel, would be an answer if the FC were well tuned and had LR rds. .
Iskander is perfectly good for that task, since this is one of its intended tasks and arty is extremely rarely operating in one piece standing alone.
Smerch doesn't need being "loaded already" since rounds with DPICM or self targeting subs will do a fast work on any arty formation standing still. As for guided - all of Smerch rockets are guided in fact, newer ones just offer hitting pinpoint targets instead of area ones at long range.
2S35 is hardly an "answer" since it is much further in development loop. And what having second barrel has to do with counterbattery capabilities?..
