The BSF S70 was made to shoot 11ft/lbs and has similar scale to the 335's. I don't think in this scale chamber/rifle getting 11ft/lbs does them any favours. Heck even a FWB Sport do better at a tad under rather than over 11ft/lbs.
Its not they can't be made to do more but just behave better with less.

In its day the 335 was always considered a bit low powered than the competition. In those days few people were so chrono needy, few had them and if they did it was a shop's pendulum! More importantly was could you hit something with your rifle in the farmyard. Everything else was marketing hype. The 335 certainly was known for its accuracy though lost out on the hype front. Most rifles were sold with the promise: "full power!"; but the 335 wasn't. Once out of the shop few people knew what their guns were shooting power wise thereafter.
Of note the 335's aren't "big", and are light weight. Just nice, but not super sexy "man sized".

Anyhow, the 335 had the reputation for just being a darn well made accurate rifle. The MKII's I've had all shot well, with good triggers. A pleasure to shoot. The stamped checkering was a bit ugg.
An excellent example often change hands at the £200 mark. It would need to be truly mint to do better. Sadly will always be priced below more "powerful" rifles even though few match them for outright well made quality. For the back garden then few better them for pure enjoyment.