Out of 17 delves, there are only 5 that have neither a defender or support. These are City of Thieves, Dark Pits, Sunken Fleet, The Warrens, and Werewoods.
In City of Thieves, King of Thieves is the only troop that can generate stats, and only for himself. Coincidentally, a lot of people put him in front, even though Tomb Robber and Street Thief are the ones with Agile (20% Dodge).
In Dark Pits, nothing could generate stats. Plague Rat though did have Impervious, which is pretty nice for front line, and Sledge Paw had 25% skull reduction and +6 Life per turn.
For Sunken Fleet, again, nothing generates stats, although Maraji Queen has 33% Skull Damage reduction and Crab Man has 30%. Crab Man also submerged himself to avoid damage from the enemy’s Water Elemental. I really don’t remember what I put up front for this team.
The Warrens has Lapina Knight, which has both 25% skull damage reduction and 20% dodge.
What’s really interesting is that the delves with no defenders/supports are also the majority of the delves that I have the least pure-faction renown with (Werewoods, Warrens, City of Thieves)
So what’s the difference than between Dark Pits/Sunken Fleet and Werewoods?
Hex Rat gives you an AoE with double damage on the targeted troop if they’re cursed, and death marks them. And Rattigar puts random negative effects too on enemies. Sledgepaw also gives you a semi-controlled gem destruction (5x5). In other words, the damage is very consistent.
With Sunken Fleet, Water Elemental also gives a massive AoE and stun, an empowered troop to give you mana and death mark enemies, and a doomskull generator that also starts all your troops at 50% mana.
Werewoods has no AoE damage, it has two single target damages. Its generator is color specific (explodes red gems). Only one troop starts at 50% mana, and happens to be the troop you want to use the least often (it has the worst ability).
Werewoods highest damaging ability from Werecat also has the potential to backfire tremendously, giving the enemy 4+ matches, since at its lowest, 13 gems, creating 8 more doesn’t guarantee a 4+ match to loop it.
In other words: Dark Pits and Sunken Fleet work because they are much faster, much more consistent in damage, and you can effectively kill the enemy before they kill you. The same is not true for Werewoods, it’s a gamble. Now add on top that every troop gambles itself as well with random transforms.