Attackers have several ways to deny him with the element of surprise, and can easily headshot him once they know his position. The tradeoff between his turret's stopping power and his lack of mobility isn't good enough.
'When looking at Tachanka, the biggest downside lies in the gadget. Despite being popular with the community as a design - he looks a bit like a tank - his pick rate 'is the lowest in the game' according to the design notes on the above linked patch notes. Tachanka is one of Siege's playable classes, called Operators, and he has a deployable turret. The Mid-Season Reinforcements update tweaks Tachanka, one of the game's operators, introduces a new map to PvP, and makes a number of weapon balance tweaks. Tom Clancy's Rainbow Six Siege is getting some substantial changes.
