Everyone's analyses have been so amazing and detailed oriented.
Dragalge ranked B
+great movepools with STABs which include: dragon tail, acid, water gun, twister, poison tail, water pulse, double team, toxic, aqua tail, sludge bomb, hydro pump, dragon pulse, feint attack, acid armor(breed), haze(breed), play rough(breed), toxic spikes (breed), venom drench(breed), surf HM, shadow ball TM
+available pretty early with good rod fishing in gearen sewer, you can get it even in pre Venam
+great ability adaptability, which allows STAB to go twice as powerful instead of 1.5, given most Dragalge leveling up moves are STABs, it is most recommended, poison touch/poison point on top of requiring physical contact, the chance of activation is slim
+65/90/123 are amazing bulk, can work as a tank, and whittles down opponents with learnt Toxic, acid armor could even potentially raise defense more if you breed it
+75 base attack and 97 base sp attack allow dragalge to land massive damage on opponents while tanking their attacks, it is particularly helpful in Crawli's battle and Valerie's battle when it stays as a Skrelp
+unique typing with dragon/poison helps with Aelita's rebattle post Angie since it resists all Aelita's movesets, Skrelp's poison/water typing also helps with couple of major NPCs like Rorrim B
-the reason it is not in A rank is because it stays as Skrelp throughout most of the current game, which is quite difficult to raise
-its nonexistent speed is its major flaw
-before the type changes happen upon evolution, it cant do much against early gym leaders until Crawli with mediocre stats those of Skrelp's, and of course no one with sound mind would use dragons for Angie, which leaves it with Amber and Crawli for gym leader battles
-loses water STAB with adaptability boost after evolution, which is a shame considering many of its moves are water type moves
Also, reserve Walrein for later if no one has done it already.