I'm not sure that being too close to Heathrow is the problem - it doesn't seem to unnecessarily trouble KLM, SN Brussels, Air France or Easyjet.
However, trying to grow a route like BRS-FRA in very bad economic conditions, with airfares out of Heathrow getting very competitive, is going to be difficult. The gap between ex-BRS and ex-LHR fares is growing, because the ex-LHR fares are going down (and LH's YQ isn't - hint hint).
There's traffic there to be had, but it needs time to migrate or grow - whether or not that can be sustained when everyone is bleeding ink remains to be seen. Look at what BD's had to do with LBA, MME, JER, AMS, BRU, LAS, ORD on well established routes.