For Druid + Rogue at level 1; the fight is not necessarily required.
By focusing on the thug's DPR, you, as OM, are looking at this party through a very narrow lens. I suggest that since (1) you only have two players and (2) neither of them is of an archetype of warrior, the adventures that you lead for them up to At what they reach the second level should focus more on role-playing, exploration and escape / mobility and a little less in melee. But when they choose hand-to-hand combat, they need to try to commit on their own terms. (Credit: Sun Tzu theory)
Globally, in a narrative sense, the chances that a thief and a druid will mix in the dark corridors of an underground dungeon are not very high. And, creating the adventures as suggested you make them work as a team from the start.
Beyond that, they may not need a tank to create an advantage.
How can the druid help the thief to gain an advantage?
Sometimes with the Help action, but does the Druid player adhere to this? Maybe and maybe not, but in any case it's between the two players to understand. They have to work as a team because there are only two.
In some situations, Help will be a good use of an action, in others Will not do. Let them understand this by playing and making decisions / choices.
Certain spells of druids can offer advantages. Again, these are your players who need to work as a team to get the most out of it.
Entangle (SRD p. 140)
Note that a creature that fails to save is
… restricted by tangled plants until the end of the spell.
From Annex A, conditions, restricted
Creature's attack rolls have an advantage, and the
attack jets have a downside.
The rogue attack with advantage allows a sneak attack.
Fairy fire (SRD p. 141)
Any attack roll against an affected creature or object has an advantage if the attacker can see it, and the affected creature or object cannot benefit from it. to be invisible.
Snape has the advantage, the sneak attack.
From your comment:
My players have little experience overall and none with D&D 5e. It is their wish to start at level 1 in order to keep things simple.
It is OK to coach your players if they are new; you are the MD, coaching is part of your role.
Change your DM & # 39; ing paradigm to fit your two player group
Their first level of adventure should focus on using their intelligence, not their strength, to achieve their goals. Between the druid's spells and the thief's ability to pass ability tests, and stealth around, and occasionally apply a stealth attack if someone climbs into the druid's grill, you can experience exciting and stimulating adventures without tank.
At level 2, Snape gets cunning action, Druid gets wild form; their options are expanding considerably.
Two of us played a thug game for a session (in an urban setting) to help a DM get used to managing a game. We used ranged attacks, movements and everything except melee combat to achieve our goals. It's doable, it's fun, and it's always dangerous for the PC.