I know that there is already an anological proposal, which nevertheless remained without attention.
viewtopic.php?f=95&t=27573&p=311905#p311905
I do not know why this topic was left unanswered and closed for commentaries because I ventured to make a double. I hope if the moderator finds my post a violation, then the punishment will not be too strict.
Problem.
The middle tree of engi is frankly weak. The long DPS cycle and the lack of burst damage do little effective in both the ORVR and small scale environment.
Analysis versus Magus.
RoR.builders - Magus
What makes Magus strong so is the "Indigo Fire of Change" in the middle tree that he uses as a filler during the DPS cycle. While his engineer's analogue "Focused Fire" is in the first tree and taking into account the nature of the damage, the physical against the magic one makes it weaker.
Also in each tree of the Magus there crit tactics that are convenient for accessing and in the core tactics for increasing the crit damage from the "Surge of Insanity" that allows Magus to use this tree for both AOE and ST damage. The only one crit tactic of the engi is so far in the tree that is designed to play in a well-coordinated group and does not go well with the distance the Grenadier and Rifleman are working on. Any attempt to take this tactic rests on the inability to build a complete build in both tree without losing abilities.
40/50+ rr build


Solution.

1 Swap "Phosphorous Shells" with "Strafing Run" which will be quite logical. The build of the Rifleman will get an OMG baton and still will have access to the "Phosphorous Shells" in 1&2 mix tree. Then as a Grenadier it gives a skill that fits well with a mobile tree.
2 Swap "Tracer Rounds" tactics with "Trench Fighting", making access to the crit tactic more accessible and freeing the points for creating finished builds.
When writing the text, Google translator was actively used. Please, if something is not clear in the text, let me know and I'll write it in other words.