Well, my idea was that the Warlord starts with medium armor+shield and upgrades to heavy later. Medium armor is perfectly doable at low levels even if you don't have a crazy high dex mod. But I suppose something could be worked out? It's just something where I would want to avoid a "one level dip" temptation, which getting heavy armor proficiency would do (hence why Clerics don't get that anymore, it waits for 3rd now). If a Cleric can survive two levels before getting a domain with heavy armor, I think a Warlord should be able to as well.