The lag doesn't happen only on high load times.
Per example, this morning (GMT+0) around 11am, when almost no one is online, we were lagging like hell (+2k ms delay) for like 30mins, then it went away and the game was playable again.
Sometimes it's just spikes... other times dcs...
If the dedi is in fact the best option available atm, something must be wrong somewhere.
No, its not our ISP. A quick speedtest check showed that all latency was withing the acceptable to german servers (60ms in my case).
Maybe routing problems? Like it happens in EUW (LoL)? Cause like some have said, it doesn't affect all players, and not all at the same time.