There is a client briefing by Keoghs on the effect of the ERRA at http://www.keoghs.co.uk/Liability-AWARE/Employers-liability-claims-and-the-ERR-Act
One interesting aspect of the discussion is the statement that the Regulations cannot be relevant to the issue of negligence. Keoghs state:
“Some commentators argue that breach of statutory duty can still be pleaded as evidence of negligence and the standards by which negligence should be measured. This does not however appear to stand up to scrutiny given the distinction between the common law test of ‘reasonableness’ as opposed to the statutory tests of ‘strict liability’ and ‘reasonable practicability’.”
This has to be contrasted with the statement made by the government itself when making the amendment.
Minister Viscount Younger in the debate by the House of Lords on 22 April 2013 stated:
“We acknowledge that this reform will involve changes in the way that health and safety-related claims for compensation are brought and run before the courts. However, to be clear and to avoid any misunderstanding that may have arisen, this measure does not undermine core health and safety standards. The Government are committed to maintaining and building on the UK’s strong health and safety record. The codified framework of requirements, responsibilities and duties placed on employers to protect their employees from harm are unchanged, and will remain relevant as evidence of the standards expected of employers in future civil claims for negligence”.
(Emphasis added).
See the link to Hansard here
http://www.publications.parliament.uk/pa/ld201213/ldhansrd/text/130422-0003.htm
It is clearthat the Regulations are highly relevant to the issue of negligence and the standards to be applied. See the discussion at https://accidentsatworkandlossofearningsclaims.wordpress.com/2013/09/30/the-remaining-importance-of-health-and-safety-regulations-after-1st-october-2013/
PERSONAL INJURY: LIABILITY AND DAMAGES 
Apart from overlooking Lord Younger, as you rightly observed, Keoghs are simply wrong. I cannot foresee any employer convincing a charge that any proven regular tree breach is irrelevant or should be disregarded in a civil claim. In any case, the analysis of statutory standards, and their relationship to common law duties is wrong.
Sorry ‘charge’ =Judge