Contrary to many of the reviews here, WWF is an organization which is very much "boots on the ground" - more so than most other large conservation NGOs. That's not saying they could not improve, but they work on long term initiatives, with collaborating with many partners, to make lasting impacts to wildlife through management improvement, laws and regulations, and innovative initiatives.
When considering the amount of overhead for any NGO it's important to consider this in relation to the scale of the company, and also keeping in mind that for profit businesses wouldn't be successful if they couldn't pay their employees a decent salary and spend money on research and development or training of employees or other expenses that are not "boots on the ground" but that make those boots SOOOO much more effective when they are on the ground (and make sure that boots are trampling the correct ground/direction).
Regarding the hunting aspect - well controlled and regulated trophy hunting is one of the best conservation tools out there. As animal lovers we might not like it, but this is the truth. It is incredible brave and forward thinking for WWF to be working on well managed trophy hunting for the long term preservation of species - even though people sitting in their comfy house in the US with their pets don't agree.
Too much of their money is spent on overhead and advertisements aimed at getting more donations. They do little "boots on the ground" work and some of their philosophies run counter to true wildlife conservation. EG. They actually support hunting of some endangered species. They also have a tendency to pander to govts such as the Chinese. There are many other organizations out there doing solid work in combating trafficking of endangered species. Those same orgs also more more money into doing actual work and less money into supporting huge administrative overhead.