I have been shield tanking since the beginning of the open beta, though many do not know me because im no huge forum poster lol. I'm just gonna give my two cents on AV and armor vs shield tanks. First I will start
off with AV... Enjoy!

Swarms are quite simply OP. Besides being invisible and turning corners, they cause ridiculous amounts of damage. My shield tank has passive 33.5% dmg reduction, and since explosives do 20% less damage to shields, I take roughly half damage (passively) from swarms. And I still can be soloed by one guy with a Proto swarm launcher, even if my booster is active. This is beyond illogical. Now consider the cost my tank versus the swarms, my large turret alone is worth more than 20 of entire Proto suit fittings. And of course the swarms are invisible and cover isn't an option because they just go over, under, around it or just warp to my tank in some odd way (that has literally happened to me a few times, but mainly due to lag.

Av grenades are OP. Obviously they do less damage to shields, so there's my one advantage. But Av grenades, quite simply, can be spammed. Nanohive+cover+homing capabilities make it completely impossible for me to attack a well experienced AV grenadier. They sit in a spot I can't shoot nor reach them, while throw they them relentlessly, because with the nanohive they have virtually infinite ammunition. finally the homing capabilities means they don't need to see me or get out of cover, just throw them like there's no tomorrow. And once and for all, the cost for AV grenades are ya know... Roughly up to 1000 times cheaper than my tank fitting (literally).

Forge guns is a tough one. They deal extreme damage over large distances. But did you know Proto forge guns are more powerful than Proto railguns? "Well forge guns have ammo n reload" says dummy 245. Well, according to these new charts... railguns will have ammo and have to reload. So... more power, less cost, it outdoes the railgun in every purpose the railgun has. On a side note, we have no Proto tanks, so it's not easy to judge with forge guns because the Proto ones are the only ones that truly pose a threat to me. Of course forge gunners mostly hide in cover, so we can't shoot them. Most forge gunners I know even agree vehicles are up, because they are normally full time forge gunners.

Armor vs. Shield tanks:

This is crraaaazzzzyy maaannnn!!!! But seriously, it is. I personally, cannot win in most situations against an armored rail madrugar of equal skill if with any turret. If the madrugar has blasters, however, I will win as long as I either sneak behind them, or stay at a distance with missile and rail turrets. I cannot win one on one against a blaster armor madrugar with a blaster turret of my own of equal skill unless I sneak up on them. And all comes down to this: with armor hardeners they have more passive resistance than I, their heavy reppers give more HP in a shorter amount of time than shield boosters, they have higher HP, and they can move faster, so no escape.