The Sniper's death-beam causes a freeze effect when fired if it has an even number of shots left. It basically gives the Sniper a special and very useful ability, and is great for dealing with high-priority targets. There are a number of tactical tricks you can do with this effect that can help with unusually dangerous foes, but I'll let you figure those out for yourself rather than me making a confusing and not very well worded explanation.
The Science Exo also gains this ability when it gets it's chaingun, which actually is one of the best weapons in the game. The problem of course is that it's the SCIENCE Exo, and is therefore risky to use.... you dont wanna lose your source of hacking/viruses/computer stuff.
And yeah, Expert is pretty tough to start with, isnt it? The high HP that enemies have in that mode gives it a tough learning curve, but for the most part, right now the shield values are actually quite well balanced. Though there are certain enemies with *alot* more shielding than that, such as BodyBots, that are not meant to be defeated in the normal way, so if you see something with really insane health, that's likely the case. But yes, running into things with thousands of points in shielding is something that will not only be common, but will start in the early part of the game.
One major hint for starting out: Get a couple of weapons to a damage value of over 600 (or even at 600). Make this your number one priority over everything else. Particularly for the Sniper's beam since you're using him. Boosting the Assault's grenades is also a good idea. Same for the Ninja's welder. Sniper should come first though. Try to boost the Assault's laser gun to a value over 9 range or higher as well. Not a bad idea to do this for the Science Exo also. Do these things, and you're going to find the early game to be alot less dangerous. And 300+ is a good range to shoot for with the lasers for those two Exos, but it's a low-priority task. Dont worry too much about increasing ammo just yet.
Dont worry about shields at this point. Ignore that. You'll need them, but that can wait until later. And getting the Science Bot some virus points is essential.
And finally, using the enemy bot's quirks against them is also very important on this difficulty, since they have so many advantages. Blunderbots can be made to destroy themselves, for instance. And ShieldBots are absolutely amazing if you can get them virused. They're not OP, as if you're not careful their shields are going to drop like crazy, and getting into position to virus them can be VERY dangerous since you cannot kill anything near them as long as they exist, so it's quite risky. But they're still pretty darn good.
So yeah, some basic tips there. This mode will require alot more careful thought when it comes to equipping stuff, too. As well as when buying things.
Good luck though. Let us know how it goes once you've really dived into it!
And yes.... Arcen does make the coolest things, dont they? Haha. There's very, very few games I spend as much time on as their stuff, which is really saying something considering the sheer absurd number of games that I buy all the time.