I hate to say this, but most of the structural drawings I've used have welding symbols that are thirty years out of sync with the current revision of AWS A2.4. I'm not sure if it is simply some structural detailers don't care or are too lazy or too poor to purchase the most recent editions of A2.4 to keep up to date with the most recent requirements.
When I mention to the engineers that the symbols are incorrect and I need better information the reply is usually, "You know what I need, just make sure the welders put on enough weld." Poof! Now I'm the designer as well as the inspector!
I did a presentation on welding symbols at a meeting for professional structural engineers about three or four years ago. I opened with a 5 question quiz. A simple quiz, no symbols involving complex welding symbols or multiple reference lines, and not one of them answered all five question correctly.
Since the 13th edition of the AISC Steel Construction Manual is mentioned; Table 8-2, page 8-16, shows a flare bevel groove weld and symbol which indicates the weld size (E) is a required element. While I know that AWS D1.1 - 2006 is not the referenced edition in the 13th edition of the SCM, it does require the weld size of all PJP groove welds be included in the welding symbol. This requirement has been around for as long as I can remember and I go back to the 1970's.
It is interesting that the figure 80% was included in the post, because that is about the percentage of structural drawings I see with welding symbol errors. I usually quote the figure 85%, but what's 5% plus or minus amongst friends.
So as for jumping on the band wagon and joining with those of us in the new millennium, why bother. You might just as well continue to use the welding symbols that predate the 1976 edition of AWS A2.4 and when asked what your welding symbol means, just say, "You know what I want, just do it." That's the answer we've grown accustom to.
Remember my example in a response from a couple of days ago, a 3/4 circle at the apex of the leader and reference line means........... All together now: "Any idiot knows it means almost all the way around!"
How can you expect the welder or the inspector or your customer to read your mind? Use the proper welding symbol and follow the conventions that have been agreed to by AISC and AWS. If a standard welding symbol, i.e., one that is complient with A2.4, doesn't describe the weld you have in mind, draw a cross section through the weld and provide the information needed by the welders and inspectors.
Best regards - Al