I can't publish all of my data, but i will publish my averages and results. They are very similar to NZ's.
All of my samples are based on spending an average of 1400 marks. This results in 200 T1 fused relics or 75 T2 fused relics (1425m). As a result everything is averaged in terms of relics or shards per mark.
Bartering for T1 averages 1200 T2 relics or 8.5 relics per mark.
Bartering for T2 averages 1100 T2 relics or 7.8 relics per mark.
One can save some gold by starting at T2, but for the purposes of my experiment I started at T1. Each entry includes the average per mark, average per gold. The average shards from refinement (RS) and cumulative average (total of all previous tiers) shards for those produced by crits are included in parenthesis.
Tier 1 averaged 2.1 shards per mark and 19,000 shards per gold. (3000 RS)
Tier 2 averaged 2.8 shards per mark and 3000 shards per gold. (3600 RS, 300 CS)
Tier 3 averaged 3.9 shards per mark and 1900 shards per gold. (4900 RS, 600 CS)
Tier 4 averaged 5.8 shards per mark and 1700 shards per gold. (7000 RS, 1000 CS)
Tier 5 averaged 7.4 shards per mark and 1400 shards per gold. (8800 RS, 1400 CS)
Tier 6 averaged 7.3 shards per mark and 1000 shards per gold. (8400 RS, 1700 CS)
Tiers 3 to 4 and 4 to 5 produced the largest number of shards per crit, averaging just over 400 for those tiers while averaging in the low 300s for each other tier. T6 saw a 6% drop from T5 refined shards but is statistically even in shards per mark due to the shards produced in crits.
To conclude, my recommendation is to always start at T1 and refine at T5. That will produce the largest number of shards for the initial investment of marks. One can save about 15% gold by starting at T2 while taking an estimated 9% reduction in shards. However, for saving even more gold one should eliminate tier 5. This saves roughly 35% gold while only taking a 20% reduction in shard output.