As it is now, it is statistically possible, as unlikely as it is, for an IS2 to survive 5 hours with 10 P4s hammering away at the front because deflections do nothing.
Statistically possible, but feasible? No way. Besides, it's technically possible for a Pioneer squad to beat a Rifleman squad as well, but realistically? It'll likely never happen. The closest I've seen was in the Relic OKW video where a Pioneer in Green Cover destroyed a Penal Squad charging over Red Cover. I even tried to recreate it (with even more red cover), but was unable to, the Penals won with 4 men of varying health every time. Of course, it's also possible Pioneers had different stats in the OKW video that we didn't know about, but that only supports the argument that it's unlikely to ever happen and thus isn't a realistic concern.