I'm missing something. Enlighten me please.

No I don't think any army can do that...it's not just DE that will struggle. GW have made the point that weapons in 8th are only at their best when you choose the correct target. So you pick Dark Lances for tanks and you pick Splinter Rifles for Guardsmen. If you pick all Dark Lances when you play all tanks then great...but when you play all infantry you are screwed if all you have is 6 Dark Lances.

How do you think the all infantry space marine army will fare against the 3 IG tanks? What makes you think they will fare any better than your mass heavy weapon/no infantry army?

While you are right that you weren't able to kill all of his tanks in the game I think you are missing the reason as to why you lost that game, which was the conscript squad which held the objective and additionally chipped away at a whole heap of your units.

If they weren't holding their objectives and you got them instead the game would have had a different result.

With this in mind, and note I'm yet to get my first game of 8th in, the ability to split fire will be a defining feature of this edition as you are now able to diversify your interests across multiple squads rather than the tank hunter ravager and the infantry ravager you can now have two mixed ravager or a ravenwing. Thus causing chaos for the opposition as they have to take down way more targets to neutralise our firepower.

I think in these ways your list has let you down as it is focused like a 7th list would be and can't handle the horde this edition allows for.

Unfortunately you can't change it for the rest of the tourney but you should destroy some new players who are hordey

I agree. The problem persists though. If I had a list with enough to kill/win against the horde, it would be terrible against most of the other lists I'm gonna have to fight. I'll try and do batreps for all the fights. 1 per week

If only Trueborns could be taken in units of 3 again... 3 man 2DL's in cover be amazing!

If i would to make a 750 list, i would spam Blasters in Raiders.