I've gotten near 90K on Bronze once with the Salarian Infiltrator. You just need to constantly be on the thick of the action. With a low ED recharge time (mine's sitting at 2.45 seconds), you can basically just spam it anytime and with it's huge area (3 meters, if you go for that upgrade), you can constantly hit a very large mob and get a huge constant influx of points, either from assists or kills. 

On that 144K point run, we basically stayed at the center of the main building, that gave us a good control over the incoming enemies, but since my team sucked big time (heck, one of them was a N7 ranking 54 or so), they only stayed defending the corridor where the majority of the enemies was coming from, not giving a damn about the other two exits, so it was up to me to defend them both. I managed to stay alive during the entire match, so that was a big bonus that allowed me to defend the team properly. 
Our biggest difficulty was on Wave 10, when it was the Upload connection at the bottom of the right corner of the map, where there's little to no protection. I stayed on the low cover corner, always switching between flanks to get the Hunters that came from the building path and open area, while the rest of the team took potshots at the Primes. 

On that game alone, I must have killed at least over 100 enemies and assisted in the kill of another few as well, because I did a shitload of Tech kills and so did my team. I was constantly getting points in the screen in the final waves, even when there was no action going on (heck, during the pause period of Wave 9 to 10, I was still getting points from wave 9).

The Vanguard is actually a lot of fun in multiplayer. I tried him out briefly on my second ME2 playthrough (I had been a Vanguard in ME1, but of course that was an entirely different class) and didn't like him at all, but with sensible teammates to back you up, revive you when you go down and provide covering fire, he's absolutely brilliant. Is that a banshee? Screw cover, I'll go charge right into her and kill her with a shotgun.

You are terrible! You are a terrible Vanguard and you make teams die on Silver and above!

I think the issue is that I am a low level Vanguard who is, in fact, so low-level that he hasn't even tried facing silver-class enemies yet.

I am fully aware that I should be charging in and taking out seven enemies with a melee attack without taking a scratch at some point, but it takes practice and ability points.

More seriously, effective use of the Vanguard is more about practice and situational awareness than it is larger tactics about power spreads.

As a Vanguard, you have one job: clean up trash mobs (and mid-range mobs when you are stronger) so your teammates can fulfill their own roles more effectively. Some will support you, some will do more damage than you, but it doesn't matter. You are the Vanguard. On Silver or Bronze you can hold one flank by yourself, and if you play intelligently and carefully then you should not be going down. You should never go down at all on Bronze once you get in some practice.

Whenever you roll Vanguard, take a Katana, Scimitar, or Disciple levelled up to X (if possible) and your recharge rate will be +191%, or thereabouts, if you take the weapon lightness path (you should). You need to be a close-range headshot machine, which will do more damageo ver time than either Charge or Nova. Close range headshots with any of those guns will stagger most enemies, including Pyros, allowing you to get past the cooldown time necessary to start really tearing ass.

There are people who see Vanguards as "CHARGE NOVA CHARGE NOVA CHARGE NOVA CHAAAARGE", but these people are not good at their jobs. Crowd control is necessary, and Nova's stagger needs to be timed carefully, and should not be your primary source of damage.

Also don't screw with Geth Primes, they don't give a shit about your Nova and Charge stuns them less often than it does Atlases.

Never charge a Banshee if she's facing you, they have frames where they'll automatically grab you if they see you.

Man, never try going up against a Banshee if your game has a bit of lag. I was grabbed by one when I was in cover and she was still a few good 10 meters away in my game, but probably she was already breathing down my neck in reality XD. 

But that strategy you deploy is the same as mine. With my trusty Eviscerator X (or Disciple V, or Claymore II, but mostly the Eviscerator for recharge time), I usually just go for the HS most of the time. But there are just walls that you hit when being a Vanguard, and Gold difficulty is too much of a wall for any Vanguard IMO. 

Not at all - though, again, I tend to prefer weapons that fire a bit faster than the ones you use.

Still, Gold is not unfeasible for Vanguards. I haven't played much Gold myself, but many people are successful with the class on Gold. You just have to play smart, conservatively, and bravely.

Unfortunately a lot of people confuse bravely with stupidly, at least when I'm playing and there's a Vanguard on my team for Gold. Usually they don't last Wave 1 without dying at least once. And when it's against anything but Reapers, that can be a bit annoying since they usually get executed pronto as well. 

Personally, I prefer the Asari Vanguard over the Human ones at higher difficulties any day. Those Lift Grenades can be a blessing, especially when you use the Slam lifted targets path, since it basically does double damage. Plus LG can rip through Banshees barriers like no tommorrow, even on Gold, and can stun them pretty easily as well. 

I'm not saying it's impossible, only that it's too much of a wall for the grand majority of people that play as vanguard "LOL CHARGE NOVA URHH DURHHH". I've lasted up to Wave 8 with my Asari one and had my team not got swamped by direct banshee executions we might have won that game.

Just a shotgun? I was worried about the lack of long-range weapons and also the fact that my (only) shotgun only has enough heat capacity for 20 shots.

Thanks for the advice. I was one of those annoying all-caps people for the most part, and I suppose with all of the fun I was having I forgot that dying is bad

When you say trash mobs, do you mean in general those without armour or shielding?

Hey guys what do you think how many additional squadmembers will be aded in future DLC´s?
And who would you like as a squadmember. I would like to have a krogan again maybe the Krogan from Mass Effect Galaxy could become a squadmember. Or Major Kirahe if he survived in the first part.