My take on Morde's build is this
If you have a reliable team build:
Sterak's Gage 
If you have an unreliable team build or the team has far to many wall hoppers / dashes:
Full AD Team swap out merc for Tabi and visage for raudins.
Full AP swap out dead man for abyssal and Sterake Gage for Rylais.
The first build should make sure you have well over 500 movespeed while roaming with another champion. And 40% cdr will mean your speed boost only has a CD of 4.8 seconds.
If your team either lacks CC or there is simply to much mobility to combat them by running at high speed Rylais comes in. Build one should be higher dps and more survivability however. The gage alone with proc a shield that is over 1000 at full build and make Morde Base AD 210 meaning very hard hitting trinity force hits.
Runes
For my preference I would use runes to solve my CDR itemization woes, add scaling defense, or both.
9 flat attack red, scaling armor yellows, 15% cdr over time blues, 15% cdr over time quints. That's 30% cdr( spirit visage takes this to 40% end game), 9 attack for last hitting early, and 27 extra armor.
9 flat attack reds, scaling armor yellows, scaling Mr blues, 15% cdr over time. That's 15% cdr ( +15% from ionion boots and +10% from visage for 40% CDR, but no more 35% tenacity from merc), 27 extra armor, 27 extra MR which lets you drop the merc treads with no real change.
Masteries
I find masteries to be the most interesting point of discussion. Since morde can once again spec hybrid, is melee, and he utilizes both sources of damage he can gain the highest % damage modifier the offense tree offers. That is a potential 13% increased melee damage and magic damage against any champion at 50% health or lower. Also the 5% bonus stat from AD and AP scale 1x, 3, and 9x making them far more valuable than on other champions due Mace of Spades.
That is just the offense tree however. Morde's Q allows his to do well over 1k damage with only 1 damage item mid to late game. At some point damage reaches a thresh hold where adding more is superfluous. Morde may very well benefit from higher scaling defenses the Defense tree offers instead of the Offense tree.
Lastly the Support tree allows morde to cut out 10% CDR( support + offense synergy) from his itemization, increase his gold per second and per attack(bandit procs), and reduced item cooldowns by 20%. Morde new builds may very well include 3 or more items with cooldowns. He could be saving a lot of time between activations if he uses the 20% item reduction passive.
Conclusions
Mordes build will adapt solely on the ability of his team to work together and secure targets. If his team is unreliable in that function he needs to itemize into securing kills. He benefits a great deal from hybrid items and items that offer damage + health. All of his defensive items should come with health now as it synergizes with his shield. Attack speed is no longer a functional stat for him past 1 attack a second and this is achieved after simply buying a triforce. CDR is Morde highest DPS stat much like now where CDR out weighs penetration in any fight that lasts past 3 seconds. 40% CDR should be a goal for a majority if not all builds in my opinion.
= GOOD MORDE SUPPS
