For my DC, I too thought what good was a LA witness who hadn't met my DC. However, shortly after they sent in the witness form to the Tribunal with the name on, the LA contacted me and the witness (ep) will now be assessing my DC in the next few weeks.
It was pointless refusing it because the LA would just have got a Tribunal order to overrule me.
Our LA sent in a SALT who had met DD on 2 previous occasions in the past 4 years and never for therapy, only to assess on the first occasion and then to briefly feed back to the school informally on the second. The LA brought her in with under 2 weeks to tribunal (having previously said another SALT was coming) - she went into school with my permission (I couldn't realistically say no) and watched DD in class and then wrote a report which was accepted as late evidence by tribunal. On the day the tribunal pulled her apart. She totally admitted that the NHS had left our daughter with pretty much zero support despite her known needs and when pushed pretty much admitted that their recommendation for the amount of SALT in the statement was based upon resources. We had similar from the NHS OT who only saw DD because we pushed the LA to get an assessment done. We had private OT and SALT reports. The tribunal also pulled the NHS OT apart. We were awarded everything we asked for based upon our private reports including direct SALT and OT. It was frustrating to have all these games late on and I freely admit freaking out about the late SALT report when I saw it, but in the end the tribunal knew the LA games and we didn't need to do any finger pointing. Perhaps the odd hint was put in tactfully in our evidence about how bad things had been but the tribunal worked it all out pretty well. Don't despair.