I'm not going to explain which end of the sword you're suppouesd to hold, but what EXACTLY can you do to profit your team the most.
And, just a reminder: Your kills don't affect your reward in a slightest way.
Archers, Crossbowmen, Throwers
Now, ranged and DTV are love/hate relationship. From one side, bots never try to dodge your arrows, get stuck just as they're told and have big fat heads just made for headshots.
From other side, ranged bots always aim at enemies who are visible for them, which most often means that archers and crossbowmen will be first put under fire, especially if they occupy places like roofs or any other high shooting positions.
Very nice example of DTV archery are Quincy clan people, who often stand in a line of 5-6 archer and concentrate on single enemies or their groups, effectively weakening them and taking many of them out.
Throwers should consider taking a ground-level position for easier aiming, as their weapons usually have much shorter range.
Very nice guide, reading this kinda reminds you that there are people who dont take all that for granted.
Also from an archers point of view:
I am playing DTV for a long time now and can tell that almost all of the times a team loses, it is because melees pick fights they cant handle.
Most of the times when a team loses it looks like this:
All the bots are stuck under a roof, they have no ranged and pose no threat if approached carefully. Logic would tell us that ranged would simply headshot them all and so clearing the wave with 0.00% risk taken. What usually happens though is that one or a few melees dont know to do anything better than charging the whole blob, die in a matter of seconds and thus lure them all to virgin at once.
So please, if you see a blob, dont mindlessly run into it. Approach very slowly until one of the bots turns towards you and then get some distance again immediately. This way you will be fighting one or maybe two at a time and not the whole blob of 10 or 20.
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... make sure to only shoot into melee if you can assure not to hit a teammate, as in, if there is a train, aim at the bots that are farthest away from your mate and not the one clostest. If there is a 1 v 1 between a bot and a teammate, better dont shoot at all. Even bad players can handle a single bot and shooting in there holds a significant chance to get your teammate killed, as hitboxes are super buggy in DTV. If your mate dies in a 1 v 1, well then he most likely wasnt worth it anyway.
Shielders
Crowd-controlling functions, like luring bots into corners, helping in shieldwalls and shielding archers/trying to get enemy ranged attention, those are your main tasks. Of course it doesn't prohibits you from taking part in fighting, but having 20 archers concentrate on you instead of on other players really helps the team.
Two Handed Heroes
Hold your horses, charging at the enemy like you do on Eu_1 isn't going to work here (not always, anyway). First think, compare your weapon length to your enemy's weapon, then eventually try to strike them from flanks or circle and attack from behind, if you can get into a good rhythm you could put down countless enemies just by smashing their heads. On higher waves, consider using blunt weapons like Morningstar, as it deals more damage to heavily armed opponents. Or just take a Flamberge and annihilate everything that gets into your range. Can switch roles with Polearmer, depending on weapon's range.
Polearmers
It could be just my observation, but crowd-control in-combat (taking on dozen of bots yourself) is easier using long, even if a bit slow, polearms, than with two handed weapons. Also a good spearman in fence can make a huge difference, staying safely out of bots range and just stabbing them. Same in huts, having more range minimalises the change of getting struck by an enemy, while staying in safe distance and hitting them.
Cavalry
You like it rough? Fine. Only waves when you can be 100% of yourself are Nomads and Rohirrims, and keep in mind that horses die every wave. Don't expect an easy life on DTV servers if you're a cavalry player, UNLESS you can just go polearmer-piker mode.
Althought, sometimes you'll be blessing for your team when you'll chase down last cavalry bots running from players. Keep that in mind.
Peasant
Yup, its a class of its own. Thats what you are when you're too weak to kill the enemies, or you're risking dying on one hit. You should just stay at the virgin, or in places like huts, hay stacks or roofs and try to survive, so you don't lower the reward people will get. Take a Scythe, for example. Good, long-range weapon, best for peasant EVEN IF you aren't a polearm player.
Now, keep in mind that I wrote those suggestions here out of my OWN observation, its not obligatory and shouldn't be, as often there are archers who bravely saved virgin by going into melee, or two handed heroes killing last few bots with a crossbow, while lying wounded inside of a fence. :D