Just wondering if such a thing exists.
As far I know, warrior has some builds.
Have you checked metabattle?
Spellbreaker is extremely fun for roaming. Core warrior as well. I’ve also encountered multiple rangers, druids, soulbeasts, eles, guardians, holos and scrappers. Lots of variety out there!
Literally every class has one. Yes, even rev.
In terms of "easiest potential" and what I have seen fighting against them, spellbreakers (down to core warriors) and druids rule the roost. Others have to build for more damage and become more squishy in turn (instakill weavers being the most extreme).
Like Dawdler said every class has one. Most of the ones you'll outside of mesmer and thief are warrior and ranger.
Group wise, 2-5, it more depends on who you go with. Some really fun builds that have glaring solo weaknesses that are offset well with small groups.
Spellbreaker is a stealthless option but relies on kiting and running away quickly when you see an enemy zerg or far too many approaching. Can win outnumbered a lot easier than other classes because it's got a lot of damage mitigation. This is getting nerfed next patch though.
Druid has lots of stealth, you can go cele for well rounded stats, minstrel and never die or marauder burst and be able to run and stealth away from a lot of enemies. CC can be a major weakness of the druid though so CC heavy enemies you'll want to kite and be on your guard for. Also can go double signet of stone for 12s of no physical damage but it's being nerfed next patch.
Holosmith has lots of options as well as insane damage and great escape with rocket boots. If playing purity of purpose and elixir gun you can cleanse and support allies really well while also booning yourselves up to really high levels. In my opinion it's one of the most versatile roamers there is and can adapt to most situations if you know it's kit well enough and has melee and ranged options which is always a good idea.
DH still see some roaming about, can be really annoying to mesmers and thieves and can do some pretty sick burst combos but has limited escape. Check out Zodin's videos for ideas on how to play it and builds.
Necro: Search for Holt's videos for info on this, you can roam as necro but it's not going to be a walk in the park.
Rev in it's power build is REALLY good vs power classes when you figure out your weapon and legend swaps/skills but it is beyond terrible against conditions. If you see a condi build you have 2 choices, burst it down or run. Condi rev needs babysitting but can be decent in a small condi group as it pulses loads of torment which can be difficult to see.
Ele you can roam with but a scourge will make your life miserable and it doesn't fair outnumbered that well against competent players. You'll also never catch up with a mesmer and thief who can keep resetting till they kill you or you have to WP away. D/D hasn't faired that well against the power creep, I know Seven says it's fine but it's very easy for small "roaming" group of 2 scourges to render you useless as all you can do is sit out the fight till the AoE stops...which it doesn't and scourges are really prevalent. Cellofrags sword build has a lot of sustain and pretty much relies on the insane healing and dodging power of sword weaver and then outlasting your opponents.
Is damage too high?
atm no class can fight against mesmer and thief, cause they are simply the most potential classes for roaming.
but spellbreaker and druid are close to them. maybe scepter ele too.
IMO, Scrapper is the best small-man roaming class solely from Function Gyro and Sneak Gyro.
When you're getting into small fights, someone is going to go down. It means you can finish a down or revive a teammate without putting yourself in a vulnerable position. Now, on top of this you also have Sneak Gyro to stealth your entire (small) group before targeting and bursting someone down. You can use that to escape, to stomp, to reposition, etc. It's on a low enough cooldown that it's up multiple times and it sticks around for half the fight if it doesn't die to aoe damage. That wins small engagements every time.