After watching that video that Nebsif linked (which I found really interesting, learned a few new things!), I must say I am even more unsure about armour than I was before.
Yeah, modern day tanks should have a steady means of defending themselves from standard RPG7's (and LAT weaponry in general), but their protection runs out after a while.
Take for example the explosive reactive armour. It can stop the RPG from penetrating the tanks armour once. After that the charges are blown, and there's no stopping a second RPG that hits on the same spot from penetrating. There's of course no guarantee that the second RPG will hit the exact same spot, so it might still take 2 or 3 rounds to completely disable most (or all) of the ERA on one side of the tank. Once it's gone though, the tank is going to have some bad luck.
As it is with APC's and IFV's, they can't and shouldn't take much hits either. They aren't as heavily armoured as MBT's are, nor are they meant to be. They are faster and more agile than MBT's, which means they have to lose the armour to attain those feats. It is not fair to place say, the British Warrior, up with the Challenger 2 armour wise. Yeah, it shouldn't blow up after one hit (it shouldn't 'blow up' at all in most cases, the crew inside should be killed) but don't expect the vehicle to completely survive a second or even third hit.
I do think that *gameplay* wise it would indeed be fun to have MBT's and APC's tracked more easily, whilst having more endurance so that aforementioned rescue operations can be conducted. However, with the way the RPG's can be resupplied in game, it will be a spamfest that wouldn't be fair towards the armoured vehicle. The team also needs to have more and more people that don't randomly take a logitruck out for l33t zn!pz0rs, as you need those to conduct repairs with.
Regarding mines and obstructions; there's something with both.
Mines, as they are, are a bit weird. Not to mention that there are different variants of AT mines of course. We are talking about mines that can be easily acquired (as insurgent) and can be deployed manually. This means they cannot be very huge (large payload) due to the weight. A limited payload means a limited destructive capability. Blowing up a HMMWV or any other car when they drive over them: Yeah, without countermeasures it is completely possible. Normal AT mines (as used in PR) can easily toss a HMMWV 5 to 10m away from it's current position. (from what I've read anyway, people might want to correct me on this). But destroying armoured vehicles? I don't think so. While they do have significantly less armour on the bottom of the vehicle, there is still some. If a mine with a shaped charge is used, it can have a quite devastating effect on the crew/passengers of the APC in question, and for the tracks which would be torn off. The actual hull of the APC wouldn't really be damaged I reckon, aside of the bottom where the charge hit. So again, the blowing up when driving over a mine is overdone. The same goes for tanks. Their tracks will get damaged, but the tank wouldn't blow up when driving over (in comparison) such a small mine.
Deploy-able obstructions by insurgents would create too much of a nuisance. Look at Ramiel for example. There's already piles of burning filth and tires. Adding even more obstructions to that map would be insane. No single HMMWV will be able to get into the city. And why would you want to keep an APC out of the city anyway? As soon as they enter they are much more vulnerable to an ambush as they are in the open. When I am an APC driver I really refuse to go into an urban area unless I got plenty of support of infantry (checking for bombcars/RPG ambushes) and possibly/preferably a Kiowa scouting for even more bombcars

On the other hand, if those obstructions were used properly.. they could be worth it. And by properly I mean not keeping people out, but keeping people in.
It's definitely worth discussion, but it's only a game, and we can only take it so far on a computer..