Where as most rogues look out for just themselves, using other's to further their own selves, Rebel Leader's look out for the underdog. He can not only take advantage of oppertunities, but he can also create them for allies. The Rebel Leader still lives in the shadows, but he also lives boldly, giving people hope to fight on. Fighting against the powers that be while encuraging others to do so as well.
Level 3:
Bonus Proficency: You gain proficency in medium armor, shield. In addition, you can deal sneak attack damage with any 1 handed melee weapons.
Team Attack: As an action, you can create an opening for an ally against an enemy within 5' of you. One ally can make an attack or cast a cantrip as a reaction against the target. If your allies attack hit's the target, or it fails the saving throw, you can add your sneak attack to their damage roll. This counts as your sneak attack for the turn.
Level 9:
Cunning Help: As your cunning action, you can take the help action. When you use the help action to help with an ability check, it applies to a number of creatures upto your Charisma modifier.
Level 13:
Combat Leader: You and Allies within 30' of you gain a +3 bonus to intitive checks.
Level 17:
Supreme Teamwork: When you use team attack, upto 2 allies can use their reaction to attack or cast a cantrip. You can still only apply your sneak attack once.
Under "Team Attack", did you mean for the sneak attack dice to be added to any ally's attack or just the reaction-attack you create an opening for? You might want to change "In an ally" to "If that attack". It seems a bit underpowered... you can use your own action to attack with a chance for SA damage or you can use both your action and you ally's reaction to do the same amount of SA damage. Maybe you should also give advantage on the attack or add your proficiency bonus to the roll or something?
SterlingRat wrote:
I would have something like Coaching: you spend an action and all allies in a 10 foot radius are proficient in one skill you are for that round. To me that seems like a very 5e-ish addition to rebel leader/warlord.
Mechatarrasque wrote:
Level 17 is horrible. First, it fluxuate in utility with the number of melee characters you have; in a party with a melee Battlemaster, Rebel Leader, Evoker, and Light Cleric, there is no benefit. It also requires everyone to be gathered around one person to beat up, which is not exactly possible in a lot of situations.
Secondly, this is supposed to be the epic level milestone. The big leap in power for the rogue. The thief can attack twice in the same turn, plus a potential three opertunity attacks. The assassin's strike gets a huge upgrade in damage. The arcane trickster can steal spells cast at him, which is pretty common at epic level. The rebel can... use up everyone's reaction, when by this point they likely have other things to do with their reaction?
Mephi1234 wrote:
I'm assuming you're trying to build a variation on the lazy'lord, so I'm going to suggest one of their AoE style effects. "Hit everyone in this area spread."
Mephi1234 wrote:
I like this. Simple, yet flavourful. Not crazy about the name. Thieves are great at stealing, assassins murder people, what does a rebel leader do? I'd like a name that conveys leadership and teamwork without also suggesting you have to be in a state of rebellion against something. Tandem Sneak? Maybe something simple like Capo? Dunno. It's probably fine as it is.
Yeah, I'm also fuzzy on what Team Attack is meant to do. Instead of my Attack action (which would allow Extra Attack if I multiclassed for it, and all manner of bonus action attacks), I eat my action and my ally's opportunity attack (i.e. all of their stickiness) to let an ally do only what they can do on an OA, against an enemy I necessarily already had SA against. Casting a cantrip might be a benefit eventually, but it seems...iffy.
(Edit: not "necessarily." Point stands.)
I'd maybe suggest some kind of positioning-changing abilty, that happens to also provoke OA if used correctly. Maybe something like a CHA-based opposed check (but not a skill check; Expertise would trivialize it) to make the enemy move 10 or 15 feet. You trip them, bluff them into retreating, etc. Chance to provoke OA more than once, but a chance to fail as well.
Or, when you take the Attack action, your ally can attack instead (with a single weapon attack or cantrip). Either can trigger SA. You still get your bonus actions, but you get to synergize with allies as well. The level 17 feature might let you give up an attack to make all allies in X range (20ft?) attack. Just spitballing.
I would change the lvl 13 & 17 abilities to CHA mod rather than a flat #. Otherwise a solid concept Mellored!
When you are ready to post a playable character with this concept, you should name him "Wedge Antilles." 
1.) Sneak attack is weapon neutral already.
2.) medium armor? shields are something a rebel army would have an easier time using and moving
3.)Team attack, if your ally gets sneak attack do they add yours in addition?
4.) Team attack, cantrip > most weapon attacks
5.) Does the enemy need to qualify for you to sneak attack them normally or is your sneak attack automatic if you use this ability?
The cantrip problem (at higher levels it's better than a weapon attack) can be solved by saying the cantrip is cast as by a first level caster.