Heavy Vehicles, teching in 1v1

I played a 1v1 game yesterday on Langreskaya winter, and my soviet opponent managed to get an ISU-152 on the field when I only had a P4. I had to say, I was winning, but I never knew it. When the ISU-152 came out, after looking at the replay, my opponent only had two vet 3 guards (although he was floating ~2000 MP due to a sniper + SC start).
Overall, I had more fuel income than he did, however, the manpower drain I suffered as a result of the snipers (men retreating through deep snow...) cost me the game. When the ISU-152 hit the field, it's first shot killed a full health AG squad... the second shot killed a full health Grenadiers squad, and soon after another AG was killed. It was extremely infuriating. I almost killed the ISu-152 with a P4; I got behind it while a friendly gren squad engaged the AT gun. With only one man left on the AT gun it fired (I think that was a bug; when weapon teams have one man, they run away, right?) and killed my P4... then he got another ISU-152. Against two, the best strategy is to surrender. Perhaps heavy vehicles (Elefant, Tiger, ISU-152, IS-2, and maybe KV-1/8 should be limited to one at a time in 1v1 games?
I think that was the reason I lost the game... I had plenty of fuel for three panthers, but not the manpower. I didn't realize how few squads he had left and how little resources he had (besides manpower). In 1v1 I find my teching to be slow. Although the new patch helps my infantry out, getting armored vehicles to me seems an unnecessary MP cost because I am generally winning my engagements with infantry, so why get vehicles? Is there something I need to do to get them faster, or is it simply actually realizing that I can get vehicles and that I should get them?

If you forget about vehicles it helps to have a callin.
Or, when I plan on NOT getting tanks, e.g. only playing with infantry and paks, i often get a commander with either the Pak43 or the elephant and use them only for AT. Against Su85s Panzerschrecks are good enough, if you have no tank yourself the SU85 can't do much. Against T34 Paks+Schrecks+Mines should do it. And the Elephant owns ISU-152s.

Its a good backup plan if you don't build vehicles yourself.

If you found from the replay your oppenent had so few units and that you could have attacked him earlier and won I would suggest using a commander that has recon or using something like pios to find what the enemy has got and attack where the oppenent has no/very few units. I also think that keeping track of your oppenents units might help, if it has been an even fight and after about 10-14 mins they don't have a tank from a building I would be prepared for a call in tank and get some form of AT. Mines, AT guns, faust/AT nades, more tanks (if possible)

If you are wining the infantry battles you sound like you have desent infantry mirco and so try to flank around where the sniper is then use other infantry to try and force a retreat from the sniper and then use the flanking squad to kill the sniper on retreat. Just running at a well microed sniper well just loose you man power. Mortars also can be usefull against snipers.

However I do like your idea of a limit of 1 heavy call in tank at a time.

^Thanks for the suggestions guys... It seems silly to me to rely on doctrine only AT, as for Germans, the Tiger at 720 MP and 200 fuel seems like quite a lot. I don't remember how much the elefant costs, but that is only in one doctrine.
On Minsk Pocket I successfully fought of a T34/85 horde with two paks...they even were great counters to the snipers he sent out for some reason. I find mines expensive and prefer infantry upgrades but they do help in certain situations...
At the higher levels of play, I see the triple sniper/guard opening more often than not. It's hard to deal with early game