Probably not. “Too many cooks spoil the broth.”
Sometimes a client will ask if it will be helpful to hire an additional SEO company, or a few extra individual SEOs, to help with all the work. This usually means we have failed to educate the client on how it all works, or we have not had that conversation yet.
Much of the “work” involved with SEO is analysis, and strategy development. Unless your multiple SEO services are working closely together, the chances of any two coming up with the exact same strategy or even the same data from analytics is pretty slim. SEO is more of an ongoing process than a list of labor intensive tasks. Good SEO is a long term endeavor – a marathon not a sprint. When it comes to the actual work of optimizing the site’s code and content, it is unlikely that using more than one provider is going to work since each will have different ideas about things like page titles, structure & navigation, and the details of the content publishing strategy.
During the early stages of a campaign, clients will often learn that some of their competitors have many more backlinks than they do, and assume that we need as many people as possible to help get caught up. Good intentions, but it doesn’t work like that. Even if the quantity of links was as important as the quality, getting a lot of links in a hurry can be a signal to Google’s algorithm that you are trying to manipulate the search results.
Even if one SEO is handling on-page and content, and another is handling link building, the overall strategy and timing of everything is going to be off the mark unless everyone is working together closely. Multiple SEOs or link builders can also make it difficult to know who is responsible for success or failure. When your site is doing well, it would be nice to know why. When your rankings are dropping like a rock, you really don’t want to have to figure out who is responsible for all the spam links that none of your SEO people said they would use. You will end up needing another independent SEO Auditing Service to figure out which one of your SEOs is doing more harm than good – AND have to clean up the mess.