UPDATED: This is far easier than I realized. You can use the same tank, on the same map! (Thanks GameGod03!)
**Note: I originally wrote this for the Xbox One version--if you find an discrepancies, please let me know! I haven't been able to find any**
You'll definitely want to combine with this achievement to save time:
There are 7 different Proving Grounds game types.
With my re-testing of the maps, I tried out a couple different ones.
I believe Standard Battle is fastest!Use Tier 1 tanks--I used the T1 several times as well as a couple other Tier 1 tanks that didn't work as well. The NC-31 and MS-1 worked well though!
The reason Standard Battle works so well is your teammates are all Tier 2, and all enemies except for one of the last are Tier 1. Your teammates can really help clear the map for you!
Each map didn't take me longer than 5 minutes, with the fastest around 3.5 minutes.
And a few pointers to watch out for with Standard Battle enemies--they are the same enemies, in the same places every time. I ended up going through the middle of the little village to take out the LTraktor first--he'll shoot at you, but if you park just below the ridge, he'll always hit the ground.
Then I moved up, took out the FT fleeing back to their base on the left side from the 2nd group of enemies spawn.
Next, I would move towards the base--be careful here though! A Medium I and NC-31 spawn and move towards the front of their base and can do a lot of damage. I recommend hiding underneath the cliff near their base ASAP and waiting for your teammates to kill them, or carefully pop out and kill them. Remember, they will always shoot at your center of mass, so you can stick out and shoot them quite safely!
For the last part, the big worry is the far right side. First there will be a LTraktor, followed by a T2 Light. Both of these can do a lot of damage. I recommend helping kill the LTraktor, then running back down the hill in front of the enemy base and let your teammates kill the T2 Light.
That's what worked for me most effectively.
Any suggestions as to what might work better? Let me know!
Old achievement info:
*** Spoiler - click to reveal ***
I only did these 4 for the achievement:
Assault(Defense)ime
Island Race
Assault(Offense)
Battle for Mines
Skipped were:
Standard Battle
Encounter Battle
Hunt the E-100(DO NOT DO THIS ONE--you have to have a high tier which will not count for the other achievement).
The best pointers I can come up with are to use a tank with a very strong gun, for potential 1-hit knockouts, so you can hide, roll out, shoot, and hide again if necessary. I found what killed me most often was just losing bits of health over a long time.
Use a Tier 6 tank or lower so that you can get the other achievement at the same time. I used the German Tier 5 Stug III G with the 10.5 cm cannon for all 4 games. It handled really well with it's frontal armor and heavy cannon package.
For Pacific Race if you do that one, you should know--there is an invisible 15 minutes timer that will fail the mission if you don't complete the race. Also! You have to kill ALL enemy tanks as well. That made me restart this mission several times. Try at all costs to stay up with your team. If they get too far ahead, they won't be able to help out shooting at the enemy tanks(that only show up when you get close enough) and you'll get stuck far in the rear painfully shooting tanks solo. (15 enemy tanks)
With the Assault(Defense), a heavy one-shot type gun worked great for me. Just keep killing enemies as fast as you can, that way your teammates will be able to survive and eventually just outnumber the enemy. When the real heavy tanks start showing up(for me in a Tier 5 there were KV-1 tanks) let your allies take them on first, then ambush them from the rear so you survive. (At least 15 enemy tanks)
Assault(Offense); in my Tier 5, I got shotgunned by an enemy artillery first time.. very embarrassing. Watch out for them! Wait for the artillery to fire, as they will fire into the ground at you even if they can't hit you, then pop out and shoot them. There was also a KV-1 posted guarding the right side, so I flanked around him. Something to remember, your allies will move up to take the base, but ONLY after you have moved inside the base circle. So, if you can sneak into the enemy base circle safely, then back off and hide, your allies should be able to help you finish it off very nicely!
Battle for the Mines I really don't remember at all, so it must have been an easy first try. If you have any notes to add about it, please comment! 