Detachments Strategy

So I try to always play in Detachments when I am on unless I am pressed for time, so I have a decent amount of experience in them playing in them as well as commanding them. And I have been thinking about the strategies we use in it as well as tier 6 CW. So I know that a while back we decided to use the 5 LT 2HT strategy. I have found that at least recently an all speed team with possibly like an m6 for fire support has been working better. Most of the time the HTs simply take too long and their armor doesn't even count as almost every team immediately loads Prem rounds when they see a heavy. I have found that the added flexibility of the fast tanks as well as their superior ability to swarm and regroup far out ways the possible benefits of the armor which rarely is effective. Heavies are not necessarily obsolete. Sometimes an m6 or the like with their acceptable speed and higher alpha can be useful in taking apart teams that are camping. Often recently teams have brought O-Is which have armor which can be difficult for many tanks to pen even with prem rounds however they are just so slow and their guns are so derpy that the only consistent strategy with them is to take like 4 or 5 O-Is and hide in a corner and derp anything that comes. Competent speed teams can usually take them out be killing scouts and then picking off the O-Is. So if you don't camp (which isn't ever really a good choice only a last resort) with heavy tanks it is often difficult to react to what the enemy does. Basically I have found that heavies don't really provide benefits and that fast high DPM tanks are able to win any scenario while heavies are frequently map specific. Please tell me what you all think and whether you agree or strongly disagree. Just some observations of mine.