Yes, primary sources are always best, but there aren't very many primary sources to work with, at least not easily available, and numerous contradictory secondary sources. I was trying to point out that with just a few primary sources we can sort out which secondary sources are more reliable.
Talbot died bef 26 Feb 1311.
"the heir of Sir Edmund Talbot" & "Joan, late the wife of Edmund Talbot" [http://www.british-history.ac.uk/inquis-post-mortem/vol5/pp153-164]
All sources seem to agree Dutton died c. 1326, but he was most definitely dead by 12 May 1328, and Thomas was still under 21.
"Grant to John Wyard, king's yeoman, for his expenses in the king's service and for debts due to him by the king, of the custody of the lands and tenements late of Hugh de Dutton, tenant in chief, during the minority of Thomas, his son and heir, and, if he die, of the custody from heir to heir." [http://sdrc.lib.uiowa.edu/patentrolls/e3v1/body/Edward3vol1page0330.pdf]
The window for Radcliffe's death is 1357-1361, only 4 years, definitely by 1362, when son Richard holds his father's property.
So, the husband order seems clear. The secondary sources giving 1. Talbot, 2. Dutton, 3. Radcliffe, would be right, about that.
There doesn't seem to be a primary source saying Joan was such and such an age, on such and such a date, but, based on that husband order, and her supposed children, we can narrow the window for her birth date.
5 kids, after 1326, at a speedy rate of 1 per 1.5 years, is about 1333.5 for her last child. The average natural cut off is about 40 yrs old. 1333.5 - 40 = 1293.5. 4 children before 1312, at the same rate, would have her married about 1305 and starting to have kids in 1306, at age 13/14.
Marriage 1: c. 1305 at 11.5 yrs old; child 1: c. 1306.5 at 13; child 2: c. 1308 at 14.5; child 3: c. 1309.5 at 16; child 4: c. 1311 at 17.5
Marriage 2: c. 1312 at 19.5 (appears to have taken a more leisurely pace of a child every couple years)
Marriage 3: c. 1326 at 32.5; child 1: c. 1327.5 at 34; child 2: c. 1329 at 35.5; child 3: c. 1330.5 at 37; child 4: c. 1332 at 38.5; child 5: c. 1333.5 at 40
Primary sources cited as supporting her first child being born c.1306/7 is the Inq p.m. of Henry de Shuttlesworth, in 1326, which states her eldest son, John Talbot, is still a minor, making him max. 20 yrs old, and a land grant, in 1328, indicating he was 21 by then.
Born c. 1290 would allow that maybe she was extra fertile and had 1 or 2 after 40, 43/44 at the latest. Born c. 1287 is still having kids at 46/47. I thought 43/44 was pushing it, when I gave the c. 1290 birth date. 46/47 still seems a bit much. Born c. 1273, married to Dutton first, and the other two after 1326, was having 9 children after the age of 53, and impossible.
The marriage order also gives us birth ranges for the kids. All her Talbot kids should be born by1311, all her Dutton kids 1312-1326, all her Radcliffe kids 1327 or later.
There seems to be an issue with some Radcliffe children. If they're her kids, then their birth dates should be adjusted to fit in those ranges. If we're fairly certain of a birth date, and it's not in those ranges, then source the birth date, and remove them from Joan, as she can't be the mother. Using sources that say she's the mother, but then just giving the kids random birth dates that don't fit the marriage order, doesn't seem to make sense. As it is now, Julia and Richard Radcliffe are either not her children, or have the wrong birth dates.
The thing with a 1290-1293 birth date is that it makes both Roberts candidates as her father, if MedLands c. 1270 birth date was used, for him (MedLands & Richardson are both just giving estimates). However, as I included, Maud does have a primary source, for her birth date, which makes her about the same age as Joan, ruling Maud out as mother, and still makes Robert I & Elizabeth the more likely parents. As there's no account of Robert II being married prior to Maud, it makes the secondary sources saying she's the daughter of Robert II, likely wrong. It most definitely rules out Browning & Raines, or any other secondary sources, that give her Magna Carta descent, via Maud.
With just a few primary sources we can, at least, present what is more likely than not. We seem to be using some arbitrary numbers.
Whether there are any primary sources stating she is definitely a daughter of a Robert Holand, or not, is another matter.