Yeah it can be frustrating sometimes. It's funniest when I think I'm jumping my lancer or lacewing to safety and then bam! Blown out of the sky! That said, in the grand scheme of things, bots' sniping abilities is one issue I don't mind so much. Their tactics have been getting better over the years, but they are still nowhere near a human's. Their normal fire aim is also somewhat midway - good sometimes.. not good other times. So I guess it's okay that they make up in "skills" like this one.
In the past, I've had a couple of lucky kills of my own where I hit a lancer with my longarm midflight. So I know it's possible :-). And overall this bot "skill" helps me improve my own game, since I don't rely on my opponent being unskilled for me to win.
By the way, if they're hiding at the back of the map the whole game, they're almost definitely not a bot.