The best advice to always apply and see.
That being said, if Osler or something is looking to add in the articling recruit they usually run a very limited recruit for just one student. They know they will have their pick and are selective as a result.
Siskinds already filled their spots, unfortunately. I'm interested in Roy O'Connor and Sotos as well! Re: final paragraph, is it because of the heightened competition (i.e. since demand for students is low) that I wouldn't be competitive at Bay Street firms seeking to add additional articling students?
Sutts Strosberg is an unusual case because it is based in Windsor. Any reason you would prefer them over London-based Siskinds? They are probably the largest plaintiff class action firm.
Roy O’Connor, Rochon Genova or Sotos might be good Toronto based options.
You will be competitive at any firm doing the articling recruit as their main source of students (but not for Bay Street looking to add one more student). Obviously apply to all you are interested in.
Edited to add I think plaintiff firms are not looking for clerks as they are not marketing prestigious juniors in exchange for high hourly rates, like Palaire, for example, is.
If you are in your first few years of call at a major firm you should probably not be actively trying to bring in clients. Anyone who might hire you directly is unlikely to be a valuable client.
There is a ton else you can do. You can develop areas of work and referral sources within your firm, try to remain socially engaged with your law school classmates and becoming a visible and prominent member on certain client teams so you are part of the face of the firm to them.
Many people do very well at large firms without a major “direct” client base, i.e. companies where they were both the initial and direct point of contact. They do so by being a go-to-person in something (like tax litigation) for partners with clients who send their existing (in this example) tax litigation work elsewhere. If you are in a satellite office this can be as easy as being the “Ottawa guy” for enough large office partners.