I'm a howitzer user...And i completely disagree.
I think its other artillery that should have increased cooldown. Artillery non-stop spamming is never that much fun. If you want howitzers that can fire more often, get Artillery Fortification. And if thats not enough, build 2 howitzers.
It's fine where it is.
A howitzer not moving is no problem. Defend it, and your howitzer also becomes a killzone for enemy infantry. Huzza
I as i said before i think Howi cool down time is to long especiallycompared with other types of artillery but increasing the cooldown time of other arty would also slove the problem