I'd hope so, the pack howie is a howitzer that takes 3X0 manpower, a side tech, and can't hard retreat compared to a wehr techless 260 manpower unit. Not to mention pretty sure pack howie fires slower than wehr mortar.
If your gren is fighting enemy unit + howie it should lose the engagement not sure why you think otherwise. If they have pack howie they're gonna have a much smaller force due to the cost and teching, you can should be taking advantage of that.
The problem is, the pack howie basically hard-counters all of Ost's units with nearly zero user input. The Ost mortar is good, but as with all IDF units, it's best against static infantry - which USF rarely uses. Every single USF infantry unit, short of M1919 upgraded rifles, can fire on the move with little to no problem. Compare this to Ost, which is based entirely around static units: The MG42 is a core unit (unlike the .50), the Gren LMG needs to be stationary to fire, the early/mid AT role is filled by the PAK (compared to stuart, zooks) due to Muni cost, etc.
To counter all of these units, all the USF player needs to do is sit a pack-howie within range, and let it auto-fire. There's zero player input for an incredible amount of power.
Imagine if OST had a unit that auto-marked nearby moving infantry with +33% RA, forcing allied infantry to remain static; it would be absurdly OP. This is basically how disruptive the Pack-Howie/US-MHT is to OST play, except there's also doing MP-drain.
Also, I had a very similar post about this a week or so ago; there were some good suggestions by others in it: https://www.coh2.org/topic/91307/indirect-auto-fire-vs-ost