TPLink tend to be tuned for tolerance and ease of use. The most common issues I experience with them are poor latency, dropped packets and unreliability. Typically resetting the router a few times a day solves most of these issues, that and changing the channel to less used channels in your area to avoid signal contamination.

ASRock's G10 is aimed at gamers, gamers worst enemy is latency, packet loss and corruption. It would stand to reason that the ASRock router would be tuned with much lower tolerance to dropped packets and data corruption as a result. These settings would by extension decrease signal range, significantly given how aggressively I suspect the firmware rejects weak connections. It also limits contamination to an extent by rejecting weaker signals off the bat. 

I can't offer any fixes as I am not familiar with the G10's firmware but this may be of some help locating the issue, if these tolerances can be altered it should increase range the more tolerance you allow.

Basically higher tolerance = greater range at the cost of lower reliability

Lower tolerance = decreased range but lower latency + greater reliability 

I hope this is of some help. I am no expert and could be wrong but this makes sense to me.