"mild complaints" is a correct and usable phrase in written English.
It refers to complaints that are not severe or serious, but are still valid and worth addressing. Example: The customer's mild complaints about the long wait time were quickly resolved by the restaurant manager, who offered them a complimentary dessert.
This led her into mild complaints about the present art world.
One or two teams will have mild complaints, but there will be general agreement that the teams in the final game are the right ones.
Fry furiously rebutted such mild complaints in The Tribune, beginning: "We have seen it stated that the composer of 'Santa Claus' intended it for an occasional piece -- a sketch, etc.
Romania and Bulgaria have been backsliding ever since they joined the EU in January, and yet there have been only mild complaints from Brussels, which has lost the leverage that it had before the two countries' entry.
These are, of course, mild complaints about a guy who will most likely win the AL manger of the year award (especially since the Toronto Blue Jays are in danger of falling to last place without him, assuring him of many more years of booing to come).
Dr. Zinsser originally called with some mild complaints about a recent piece here on Dr. Michael Miletic, a Detroit-area psychiatrist who believes that the adaptation to early trauma is one of the survival defenses that elite athletes use to reach high levels of achievement.
I registered a mild complaint to the club management and I don't know what transpired.
At least that provided a bit of spice, with the France coach, Aurélien Cologni, mounting a mild complaint that Ellis deserved heavier punishment.
In overthrowing Amin, Nyrere has violated the Organization of African Unity's boundary rules, but only Nigeria has lodged a mild complaint.
Cone bases a speculation that Matisse "sided with the nationalism of the current Vichy regime" on a mild complaint by the artist, back in 1924, that people were mistaking, as French, the cosmopolitan art scene in Paris.
