I think DMP (Dead Man's Plate) would work better on Tahm than Randuin's, considering also the movement speed that it provides.

I personally feel Tahm would be much stronger on mid lane, with Ignite/Flash and proper use of his ult together with a teammate, especially the jungler for 3vs1 and 4vs2 scenarios on bot or top.
This requires an APC as Top or Jgler ofc, but the Items you stated in this guide look sound.

erm How about enchanted armor ?

Ive made a mastery chapter with explanation on each one i choose

hey there, good guide, what benefits can you take from the perseverance and second wind instead of recovery , also the fact that you are avoiding enchanted armor, I just played him top and love it but don't know what points in deffense to put. Keep it going!