This is really horrible rate. Are you sure there are no invalid clicks? What is that niche? I think you could try to contact AdSense team regarding this to know what is wrong.
its a trend that adsense is paying very low for last couple of days. lot of other publishers are experiencing the same. for me, its about 1/3 of what it was paying few days ago
take my example i earn 1.34$ form 52 clicks. sometimes i never make any changes, and no pr or traffic updates and ads r also same but adsense pays high. ( adsense can better know how they pay)
now 3 clicks=$0.09 (April12th) that means each click=$0.03 So 58X0.3= nearly 2.01 (+additional click from the site) Is it normal? Is there any invalid clicks?