unforetunately most B complexes dont have the proper form of B12 and even if they did they are not sublingual which means you get very little of it. Often tiles they also use folic acid as opposed to folate (ie methylfolate) which is less than ideal as well.
With the above in mind I strive to get my B12 and folate from single source products and look at "B complexes" to fill in the gaps for the rest of the B's.
On the topic of cyanocobalamin there is a lot of talk on both sides of the issue in terms of its safety. I think at the low doses found in most complexes it will be a non issue. Having said that my beef with cyanocobalamin is its simply not a form of B12 readily used by the body. It will raise B12 levels where labs are concerned BUT it will not actually do what B12 is supposed to do.
There are case studies and anecdotal evidence of this all over the net. People suffering from neurological symptoms the docs try to blame on something else. Many even tried cyanocobalamin and got no relief that further supports the docs claims. However those that were not willing to accept their fate (ie diagnosis) and continued to research often found methylcobalamin to solve their problems.
Ive been an avid weight lifter for almost 30 years now and over those 3 decades I have conversed with hundred if not thousands of people. Most of them have been on significant supplementation yet still have various issues and problems. When I question them on specifics a large majority of them get defensive because they are already "doing everything right".
Its human nature I guess, we dont like to be told we are not doing something right or the special doc we pay big bucks to led us astray but at the end of the day I am not trying to belittle anyones choices or previous nutritional path. Once I can get that thru to them, some open their mind and often find various holes in their nutritional plans and with a few tweaks here and there start to see slow and steady improvements in their condition.
If there is one thing I have learned is we are all different, we have different needs and predispositions. Supplements are also not always what they seem and many people who have used them religiously often have chosen poor forms, poor brands or simply have not used enough.
Many nutritional savvy docs actually believe that a nutritional deficiency can actually worsen to the point not only where it causes health issues but also can permanently increase the bodies need for certain nutrients.
B vits play a critical role in gut health. so they may be part of your problem or at least offer some help. You could also be in a position where permanent damage has occurred that no amount of nutrition will fix although generally speaking it can still offer some symptom relief.
My nutritional outlook is rather simple. If what your doing isnt working dont get hung up on what your taking is "proper" (ie proper form, amount) and spend all your time looking for what may be missing but spend some energy looking at what your doing and the products your taking. If your already on a bunch of supps, consider a brand change of just one at a time and see if it makes a difference. Dive deeper into the dose your taking, a great many nutrients are less toxic than water yet people fear taking too much. Not that its not a concern with some but most people , even those who heavily supplement, get far less than they probably need.
Vit C is a perfect example. Most people would say your 2g a day is a lot. For those that promote pauling therapy, they will tell you its not enough to do anything, especially if one already has heart/artery related problems.