30% to miss is quite a large probability to be honest. Most of the time people consider to-hit chances as "at X tries you will miss Y times". That will be truer(not true mind you) when your sampling universe is quite big. Such as at 10 million hits you will get closer to proposed hit chance but that might not be that visible or accurate over 100 or 1000 hits.
Also the question here is whether the hits are calculated independently or there is a mechanic which increases your hit chances at the background after consecutive misses or not. To make the hit chance more accurate even at lower number of hits some kind of modifications could be done. If they are independent...well you could miss 5 times in a row and get mad which is a very low probability but still within reason. (Vice versa is also possible)
In the end, to-hit chance indicators more like "decision-helpers" for players instead "absolute truths" (unless it is 100%) during the short time you spend on a battle.
