yes you are right,we can simply say,''employees must focus..''but still mine is not wrong when we consider the original sentence: odaklanmak gereklidir...
OK then...I'll edit your text into the way it would be more natural in English.
Sometimes being "technically" correct is not enough for a sentence. When translating we have to take into account if the words or structures used in the original would be the same a native speaker would use for the target language. If the line (even correct) sounds strange, we must change it. See what I mean?
if the original text has no mispelling, the translation is very probably like this; "It is necessary to focus on the fields where the employees think that the control is lax"