I took the initiative of reconstructing the Y-DNA R2a phylogenetic tree that was showcased here a couple of years ago. It largely agrees with UG's current cluster arrangement, which shows I worked in the right direction. With over 60 members testing upto 67 markers, the results are illuminating;
Phylogenetic tree made using McGee's Y-Utility, Phylip and FigTree. Again, I have to thank Vineviz on DNA-Forums for kindly laying down the roots for tree-building (pardon the pun) on this forum.
The Indian R2a's, who were largely absent in the previous run, now seem to be distributed across the entire tree on different branches. The preconception of Indian R2a being distinct from West Eurasian R2a was heavily supported based on the data by some (such as myself) and presumed by others.
That clearly isn't the case based on this chart. I'll have a proper look into the haplotypes later today, but this either suggests Indian R2a diversity is so great that they're quite literally omnipresent, or a hefty portion of Indian R2a arrived through multiple sources.
Relating the discussion to India, several of the clusters seem to have a combination of Subcontinental and European/Near-Eastern constituents. For instance;
o India, Tunisia, Iran-Caucasus (Aqua)
o Slovakia, India (Pink)
o India, Syria (Beige)
o India, Saudi Arabia, Scotland (Purple)
Strangely, the greatest "explosion" in R2a differentiation and growth seems to have occurred ~2750ybp. By coincidence, all of these Indian+NE/Euro clusters seem to fall after that point in time. Whether we're witnessing a real physical change in R2a's structure or an artificial construct caused by other reasons (sampling bias, program use) is yet to be seen.
To conflate the mystery of R2a further, the oldest lineages found to date seem to be from the British Isles of all places! Again, I'll have to review the data to confirm whether they actually are that divergent.
As ever, I welcome comments and appreciate the input of other users.