- Yes. This is a problem. I agree.
- I've always been on par with the rest of my team (unless I screw up and cause myself to fall behind) and am full 6 items built at usually the 35 minute mark. Soooo not sure what's happening here.
- Buy mana regen items. Oh noez, your build must has the changes.
- The smite changes are OUTSTANDING. It adds a whole new level of gameplay, forcing you to choose when to use it, when not to, how to use it, what objectives/buffs/ganks are the most important, etc. Instead of 'smite blue and red' and later 'smite dragon and baron' you actually have to choose. It takes a higher level of skill to do.
- Don't ever smite the scuttle crab. He's great for a free ward for objective control AND offers a speed boost to assist you in getting into lanes quicker. You just have to choose the right time to grab him (either befor eyou are going to try for an objective or you think the enemy is).
I see from you match history that you've played several junglers and none of your junglers have made use of the smite options. I'm actually a bit surprised to see this in a diamond elo player, tbh. Although you appear to be a lot stronger in other lanes - even looking back to pre 4.20, you still didn't do very well as a jungler for the most part. It also appears your MMR has been tanking pretty hard as of late, since you're pretty below average for your division. You also seem to never buy wards, which is also a potential issue.
In other words, I think you're better suited in the other lanes, which you seem to do quite well in. Jungle's not your strong point, and that's fine. I'm terribad as an ADC or support (except Leona). You're also a better player than me - that much can be seen by Diamond vs. Silver. You favor carries, which is awesome - and you're good with them. That's what is going to do awesome for you, so try to get carry lanes as much as you can, and leave jungling to people who have worked hard to learn the new jungle and how to utilize it. No shame in that :)
Also, good things about the jungle:
Objective control has higher significance and adds a whole multitude of possible different gameplay styles, including going solo for a delayed invade for a high risk/high reward potential first blood/buff steal.
Laners getting into lane quicker since leashing isn't as much of a thing now due to the side buffs.
Smite differentiation encouraging multiple playstyles.
Jungling not just being 'gank lanes to steamroll game' as a role, and having more depth than it ever has (while, hilariously, keeping the overall game impact about the same, focusing more on the mid-late as opposed to level 2-3 ganks). It makes junglers jungle instead of being the second or third person in every lane.